DailyCoding

DAY 1: Exactly 3 Divisors.

https://www.geeksforgeeks.org/numbers-exactly-3-divisors/

QUESTION : Given a number N, print all numbers in the range from 1 to N having exactly 3 divisors.

Expected Time Complexity : O(N1/2 * N1/4)
Expected Auxilliary Space : O(1)

Constraints : 1 <= N <= 10⁹

My Solution here

DAY 2: Modular Multiplicative Inverse.

https://www.geeksforgeeks.org/multiplicative-inverse-under-modulo-m/

QUESTION : Given two integers ‘a’ and ‘m’. The task is to find the smallest modular multiplicative inverse of ‘a’ under modulo ‘m’. If the modular multiplicative inverse doesn't exist return -1.

Expected Time Complexity : O(m)
Expected Auxilliary Space : O(1)

Constraints:
1 <= a <= 10⁴
1 <= m <= 10⁴

My Solution here

DAY 3: First Repeating Element.

https://www.geeksforgeeks.org/find-first-repeating-element-array-integers/

QUESTION : Given an array of integers, find the first repeating element in it. We need to find the element that occurs more than once and whose index of first occurrence is smallest. If there is no such element, return -1.

Expected Time Complexity: O(NlogN)
Expected Auxilliary Space: O(N)

Constraints:
1 <= N <= 10⁶
0 <= A_i <= 10⁶

My Solution here

DAY 4: Rearrange an array with O(1) extra space.

https://www.geeksforgeeks.org/rearrange-given-array-place/

QUESTION : Given an array arr[] of size N where every element is in the range from 0 to n-1. Rearrange the given array so that arr[i] becomes arr[arr[i]].

Expected Time Complexity: O(N)
Expected Auxilliary Space: O(1)

Constraints:
1 <= N <= 10⁷
0 <= Lst[i] < N

My Solution here

DAY 5: Trapping rain water.

https://www.geeksforgeeks.org/trapping-rain-water/

QUESTION : Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.

Expected Time Complexity: O(N)
Expected Auxilliary Space: O(N)

Constraints:
1 <= N <= 10⁷
0 <= A_i < 10⁸

My Solution here

DAY 6: Merge two sorted arrays with O(1) extra space.

https://www.geeksforgeeks.org/merge-two-sorted-arrays-o1-extra-space/

QUESTION : Given two sorted arrays arr1[] and arr2[] of sizes N and M in non-decreasing order. Merge them in sorted order without using any extra space. Modify arr1 so that it contains the first N elements and modify arr2 so that it contains the last M elements.

Expected Time Complexity: O((n+m) log(n+m))
Expected Auxilliary Space: O(1)

Constraints:
1 <= X, Y <= 5*10⁴
0 <= arr1_i, arr2_i <= 10⁹

My Solution here

DAY 7: Search an element in sorted and rotated array.

https://www.geeksforgeeks.org/search-an-element-in-a-sorted-and-pivoted-array/

QUESTION : Given a sorted and rotated array A of N distinct elements which is rotated at some point, and given an element K. The task is to find the index of the given element K in the array A. If the element is not present, then return -1.

Expected Time Complexity: O(logN)
Expected Auxilliary Space: O(1)

Constraints:
1 ≤ N ≤ 10⁷
0 ≤ A_i ≤ 10⁸
1 ≤ K ≤ 10⁸

My Solution here

DAY 8: Merge Sort.

https://www.geeksforgeeks.org/merge-sort/

QUESTION : Merge Sort is a Divide and Conquer algorithm. It repeatedly divides the array into two halves and combines them in sorted manner.

Expected Time Complexity: O(N) for the merge function only
Expected Auxilliary Space: O(N)

Constraints:
1 ≤ N ≤ 10⁵
0 ≤ arr[i] ≤ 10³

My Solution here

DAY 9: Union of Two Sorted Arrays.

https://www.geeksforgeeks.org/union-and-intersection-of-two-sorted-arrays-2/

QUESTION : Union of two arrays can be defined as the common and distinct elements in the two arrays. Given two sorted arrays of size N and M respectively, find their union.

Expected Time Complexity: O(N+M)
Expected Auxilliary Space: O(N+M)

Constraints:
1 ≤ N, M ≤ 10⁵
0 ≤ arr1[i], arr[2] ≤ 10⁶

My Solution here

DAY 10: Intersection of Two Sorted Arrays.

https://www.geeksforgeeks.org/union-and-intersection-of-two-sorted-arrays-2/

QUESTION : The intersection of two arrays contains the elements common to both the arrays. The intersection should not count duplicate elements. Given two sorted arrays arr1[] and arr2[] of sizes N and M respectively. Find their intersection.

Expected Time Complexity: O(N+M)
Expected Auxilliary Space: O(N+M)

Constraints:
1 ≤ N, M ≤ 10⁵
0 ≤ arr1[i], arr[2] ≤ 10⁶

My Solution here

DAY 11: Minimum number of swaps required to sort an array.

https://www.geeksforgeeks.org/minimum-number-swaps-required-sort-array/

QUESTION : Given an array of n distinct elements, find the minimum number of swaps required to sort the array.

Expected Time Complexity: O(N+M)
Expected Auxilliary Space: O(N+M)

Constraints:
1 ≤ N, M ≤ 10⁵
0 ≤ arr1[i], arr[2] ≤ 10⁶

My Solution here

DAY 12: Repeatedly search an element by doubling it after every successful search.

https://www.geeksforgeeks.org/repeatedly-search-element-doubling-every-successful-search/

QUESTION : Given an array “a[]” and integer “b”. Find whether b is present in a[] or not. If present, then double the value of b and search again. We repeat these steps until b is not found. Finally we return value of b.

My Solution here

DAY 13: Minimum Number of Platforms Required for a Railway/Bus Station.

https://www.geeksforgeeks.org/minimum-number-platforms-required-railwaybus-station/

QUESTION : Given arrival and departure times of all trains that reach a railway station, the task is to find the minimum number of platforms required for the railway station so that no train waits. We are given two arrays which represent arrival and departure times of trains that stop.

Expected Time Complexity: O(N log N)
Expected Auxilliary Space: O(N)

Constraints:
1 <= N <= 1000
1 <= A[i] < D[i] <= 2359

My Solution here

DAY 14: Median of Two sorted arrays.

https://www.geeksforgeeks.org/median-of-two-sorted-arrays-of-different-sizes/

QUESTION : Given two sorted arrays of sizes N and M respectively. The task is to find the median of the two arrays when they get merged. If there are total even elements, return floor of average of middle two elements.

Expected Time Complexity: O(log(max(m,n)))
Expected Auxilliary Space: O(N)

Constraints:
1 <= N, M <= 10⁶
1 <= arr[i], brr[i] <= 10⁷

My Solution here

DAY 15 : Sort an array of 0s, 1s and 2s.

https://www.geeksforgeeks.org/sort-an-array-of-0s-1s-and-2s/

QUESTION : Given an array A[] consisting 0s, 1s and 2s. The task is to write a function that sorts the given array. The functions should put all 0s first, then all 1s and all 2s in last.

Expected Time Complexity: O(N)
Expected Auxilliary Space: O(1)

Constraints:
1 <= N <= 10⁵
1 <= A[i] <= 2

My Solution here

DAY 16 : Different Operations on Matrices.

https://www.geeksforgeeks.org/different-operation-matrices/

QUESTION : Perform Addititon, Subtraction and Multiplication on given Matrices.

My Solution here

DAY 17 : Minimize the maximum difference of adjacent elements after at most K insertions.

https://www.geeksforgeeks.org/minimize-the-maximum-difference-of-adjacent-elements-after-at-most-k-insertions/

QUESTION : Given an array A[] consisting 0s, 1s and 2s. The task is to write a function that sorts the given array. The functions should put all 0s first, then all 1s and all 2s in last.Given an array of N elements, the task is to minimize the maximum difference of adjacent elements by inserting at most K elements in the array.

Constraints:
T <= 100
2 <= n <= 10⁴
1 <= arr[i] <= 10³
1 <= k <= 10⁵

My Solution here

Day 18: Determinant of a matrix.

https://www.geeksforgeeks.org/determinant-of-a-matrix/

QUESTION : Given a square matrix of size N x N. The task is to find the determinant of this matrix.

Expected Time Complexity: O(N⁴)
Expected Auxilliary Space: O(N²)

Constraints:
1 <= N <= 8
-10 <= mat[i][j] <= 10

My Solution here

DAY 19: Transpose of Matrix.

https://www.geeksforgeeks.org/program-to-find-transpose-of-a-matrix/

QUESTION : Write a program to find the transpose of a square matrix of size N*/N. Transpose of a matrix is obtained by changing rows to columns and columns to rows.

Expected Time Complexity: O(N*/N)
Expected Auxilliary Space: O(1)

Constraints:
1 <= N <= 100
-10³ <= mat[i][j] <= 10³

My Solution here

DAY 20: Inplace rotate square matrix by 90 degrees.

https://www.geeksforgeeks.org/inplace-rotate-square-matrix-by-90-degrees/

QUESTION : Given a square matrix of size N x N. The task is to rotate it by 90 degrees in anti-clockwise direction without using any extra space.

Expected Time Complexity: O(N²)
Expected Auxilliary Space: O(1)

Constraints:
1 ≤ N ≤ 100
1 <= matrix[][] <= 1000

My Solution here

DAY 21: Spirally traversing a matrix.

https://www.geeksforgeeks.org/print-a-given-matrix-in-spiral-form/

QUESTION : Given a matrix of size R*C. Traverse the matrix in spiral form.

Expected Time Complexity: O(R*C)
Expected Auxilliary Space: O(R*C)

Constraints:
1 <= R, C <= 100
0 <= matrix_i <= 100

My Solution here

DAY 22: Search in a row wise and column wise sorted matrix.

https://www.geeksforgeeks.org/search-in-row-wise-and-column-wise-sorted-matrix/

QUESTION : Given a matrix of size n x m, where every row and column is sorted in increasing order, and a number x. Find whether element x is present in the matrix or not.

Expected Time Complexity: O(N + M)
Expected Auxilliary Space: O(1)

Constraints:
1 <= N, M <= 1000
1 <= mat[][] <= 10⁵
1 <= element <= 1000

My Solution here

DAY 23: Max rectangle.

https://www.geeksforgeeks.org/maximum-size-rectangle-binary-sub-matrix-1s/

QUESTION : Given a binary matrix. Find the maximum area of a rectangle formed only of 1s in the given matrix.

Expected Time Complexity: O(N * M)
Expected Auxilliary Space: O(M)

Constraints:
1 <= n,m <= 1000
0 <= M[][] <= 1

My Solution here

DAY 24: Convert to Roman No.

https://www.geeksforgeeks.org/converting-decimal-number-lying-between-1-to-3999-to-roman-numerals/

QUESTION : Given an integer n, your task is to complete the function convertToRoman which prints the corresponding roman number of n. Various symbols and their values are given below.

I 1
V 5
X 10
L 50
C 100
D 500
M 1000

Expected Time Complexity: O(log₁₀N)
Expected Auxilliary Space: O(log₁₀N * 10)

Constraints:
1<=n<=3999

My Solution here

DAY 25: Maximum occuring character.

https://www.geeksforgeeks.org/maximum-occurring-character-in-an-input-string-set-2/

QUESTION : Given a string str. The task is to find the maximum occurring character in the string str. If more than one character occurs the maximum number of time then print the lexicographically smaller character.

Expected Time Complexity: O(N)
Expected Auxilliary Space: O(Number of distinct characters)

Constraints:
1 ≤ |s| ≤ 100

My Solution here

DAY 26: Missing Characters in Panagram.

https://www.geeksforgeeks.org/missing-characters-make-string-pangram/

QUESTION : You are given a string s. You need to find the missing characters in the string to make a panagram. Note: The output characters will be lowercase and lexicographically sorted, returns -1 if the string is a panagram, else it returns a string that consists missing characters.

Expected Time Complexity: O(|S|)
Expected Auxilliary Space: O(1)

Constraints:
1 ≤ |s| ≤ 10000

My Solution [here](https://github.com/iamakkkhil/DailyCoding/blob/master/Day_26.py

DAY 27: Validate an IP Address.

https://www.geeksforgeeks.org/program-to-validate-an-ip-address/

QUESTION : Write a program to Validate an IPv4 Address. According to Wikipedia, IPv4 addresses are canonically represented in dot-decimal notation, which consists of four decimal numbers, each ranging from 0 to 255, separated by dots, e.g., 172.16.254.1 . The generalized form of an IPv4 address is (0-255).(0-255).(0-255).(0-255). Here we are considering numbers only from 0 to 255 and any additional leading zeroes will be considered invalid.

Your task is to complete the function isValid which returns 1 if the ip address is valid else returns 0. The function takes a string s as its only argument .

Expected Time Complexity: O(N), N = length of string.
Expected Auxilliary Space: O(1)

Constraints:
1<= length of string <=50

My Solution here

DAY 28: Implement strstr.

https://www.geeksforgeeks.org/check-string-substring-another/

QUESTION : Your task is to implement the function strstr. The function takes two strings as arguments (s,x) and locates the occurrence of the string x in the string s. The function returns and integer denoting the first occurrence of the string x in s (0 based indexing).

Expected Time Complexity: O(|s|*|x|).
Expected Auxilliary Space: O(1)

Constraints:
1 <= |s|,|x| <= 1000

My Solution here

DAY 29: Isomorphic Strings.

https://www.geeksforgeeks.org/check-if-two-given-strings-are-isomorphic-to-each-other/

QUESTION : Given two strings 'str1' and 'str2', check if these two strings are isomorphic to each other. Two strings str1 and str2 are called isomorphic if there is a one to one mapping possible for every character of str1 to every character of str2 while preserving the order.

Note: All occurrences of every character in ‘str1’ should map to the same character in ‘str2’.

Expected Time Complexity: O(|str1|+|str2|).
Expected Auxilliary Space: O(Number of different characters).
Note: |s| represents the length of string s.

Constraints:
1 <= |str1|, |str2| <= 10³

My Solution here

DAY 30: Check if strings are rotations of each other or not.

https://www.geeksforgeeks.org/check-if-two-given-strings-are-isomorphic-to-each-other/

QUESTION : Given two strings s1 and s2. The task is to check if s2 is a rotated version of the string s1. The characters in the strings are in lowercase.

Expected Time Complexity: O(N).
Expected Auxilliary Space: O(N).

Constraints:
1 <= |str1|, |str2| <= 10⁷

My Solution here

DAY 31: Longest Substring Without Repeating Characters.

https://www.geeksforgeeks.org/length-of-the-longest-substring-without-repeating-characters/

QUESTION : Given a string S, find the length of its longest substring that does not have any repeating characters.

Expected Time Complexity: O(N).
Expected Auxilliary Space: O(1).

Constraints:
1 <= N <= 10⁵
here, N = S.length

My Solution here

DAY 32: Multiply two strings.

https://www.geeksforgeeks.org/multiply-large-numbers-represented-as-strings/

QUESTION : Given two numbers as stings s1 and s2. Calculate their Product.

Expected Time Complexity:O(n1 /* n2).
Expected Auxilliary Space: O(n1 + n2).
where n1 and n2 are sizes of strings s1 and s2 respectively.

Constraints:
1 <= length of s1 and s2 <= 10³

My Solution here

DAY 33: Anagram.

https://www.geeksforgeeks.org/check-whether-two-strings-are-anagram-of-each-other/

QUESTION : Given two strings a and b consisting of lowercase characters. The task is to check whether two given strings are an anagram of each other or not. An anagram of a string is another string that contains the same characters, only the order of characters can be different. For example, “act” and “tac” are an anagram of each other.

Expected Time Complexity: O(|a|+|b|).
Expected Auxiliary Space: O(Number of distinct characters).

Note: |s| represents the length of string s.

Constraints:
1 ≤ |a|,|b| ≤ 10⁵

My Solution here

DAY 34: Excel Sheet | Part 1.

https://www.geeksforgeeks.org/find-excel-column-name-given-number/

QUESTION : Given a positive integer N, return its corresponding column title as it would appear in an Excel sheet. For N =1 we have column A, for 27 we have AA and so on.

Note: The alphabets are all in uppercase.

Expected Time Complexity: O(Log(N)).
Expected Auxiliary Space: O(Log(N)).

Constraints:
1 ≤ N ≤ 10⁷

My Solution here

DAY 35: Reverse words in a given string..

https://www.geeksforgeeks.org/reverse-words-in-a-given-string/

QUESTION : Given a String S, reverse the string without reversing its individual words. Words are separated by dots.

Expected Time Complexity: O(|S|).
Expected Auxiliary Space: O(|S|).

Constraints:
1 <= |S| <= 2000

My Solution here

DAY 36: Check whether K-th bit is set or not.

https://www.geeksforgeeks.org/check-whether-k-th-bit-set-not/

QUESTION : Given a number N and a bit number K, check if Kth bit of N is set or not. A bit is called set if it is 1. Position of set bit '1' should be indexed starting with 0 from LSB side in binary representation of the number.

Expected Time Complexity: O(LogN).
Expected Auxiliary Space: O(1).

Constraints:
1 ≤ N ≤ 10⁹
0 ≤ K ≤ floor(log2(N) + 1)

My Solution here

DAY 37: Power of 2.

https://www.geeksforgeeks.org/program-to-find-whether-a-no-is-power-of-two/

QUESTION : Given a positive integer N. The task is to check if N is a power of 2. More formally, check if N can be expressed as 2x for some x.

Expected Time Complexity: O(LogN).
Expected Auxiliary Space: O(1).

Constraints:
0 <= N <= 10¹⁸

My Solution here

DAY 38: Number is sparse or not.

https://www.geeksforgeeks.org/check-if-a-given-number-is-sparse-or-not/

QUESTION : Given a number N. The task is to check whether it is sparse or not. A number is said to be a sparse number if no two or more consecutive bits are set in the binary representation.

Expected Time Complexity: O(LogN).
Expected Auxiliary Space: O(1).

Constraints:
0 <= N <= 10⁶

My Solution here

DAY 39: Bit Difference.

https://www.geeksforgeeks.org/count-number-of-bits-to-be-flipped-to-convert-a-to-b/

QUESTION : You are given two numbers A and B. The task is to count the number of bits needed to be flipped to convert A to B.

Expected Time Complexity: O(LogN).
Expected Auxiliary Space: O(1).

Constraints:
0 <= N <= 10⁶

My Solution here

DAY 40: Gray to Binary and Gray to Binary equivalent.

https://www.geeksforgeeks.org/gray-to-binary-and-binary-to-gray-conversion/

QUESTION : Given N in Gray code equivalent. Find its binary equivalent.

Note: We need to find the binary equivalent of the given gray code and return the decimal equivalent of the binary representation.

Expected Time Complexity: O(LogN).
Expected Auxiliary Space: O(1).

Constraints:
0 <= N <= 10⁸

QUESTION : You are given a decimal number N. You need to find the gray code of the number N and convert it into decimal.

Expected Time Complexity: O(1).
Expected Auxiliary Space: O(1).

Constraints:
0 <= N <= 10⁹

My Solution here

DAY 41: Find first set bit.

https://www.geeksforgeeks.org/position-of-rightmost-set-bit/

QUESTION : Given an integer an N. The task is to return the position of first set bit found from the right side in the binary representation of the number.

Note: If there is no set bit in the integer N, then return 0 from the function.

Expected Time Complexity: O(LogN).
Expected Auxiliary Space: O(1).

Constraints:
0 <= N <= 10⁸

My Solution here

DAY 42: Count total set bits in all numbers from 1 to n.

https://www.geeksforgeeks.org/count-total-set-bits-in-all-numbers-from-1-to-n/

QUESTION : You are given a number N. Find the total count of set bits for all numbers from 1 to N(both inclusive).

Expected Time Complexity: O(LogN).
Expected Auxiliary Space: O(1).

Constraints:
0 <= N <= 10⁸

My Solution here

DAY 43: Count total set bits in all numbers from 1 to n.

https://www.geeksforgeeks.org/position-rightmost-different-bit/

QUESTION : Given two numbers M and N. The task is to find the position of the rightmost different bit in the binary representation of numbers.

Expected Time Complexity: O(max(log m, log n)).
Expected Auxiliary Space: O(1).

Constraints:
0 <= M <= 10⁹
0 <= N <= 10⁹

My Solution here

DAY 44: Maximum subset XOR.

https://www.geeksforgeeks.org/find-maximum-subset-xor-given-set/

QUESTION : You don't need to read input or print anything. Your task is to complete the function maxSubarrayXOR() which takes the array and an integer as input and returns the maximum subset XOR value.

Expected Time Complexity: O(N*Log(max(arr[i]))).
Expected Auxiliary Space: O(1).

Constraints:
0 <= N <= 10⁵
0 <= arr[i] <= 10⁶

My Solution here

DAY 45: Swap all odd and even bits.

https://www.geeksforgeeks.org/swap-all-odd-and-even-bits/

QUESTION : Given an unsigned integer N. The task is to swap all odd bits with even bits. For example, if the given number is 23 (00010111), it should be converted to 43(00101011). Here, every even position bit is swapped with adjacent bit on the right side(even position bits are highlighted in the binary representation of 23), and every odd position bit is swapped with an adjacent on the left side.

Expected Time Complexity: O(1).
Expected Auxiliary Space: O(1).

Constraints:
0 <= N <= 10⁹

My Solution here

DAY 46: Check if two arrays are equal or not.

https://www.geeksforgeeks.org/check-if-two-arrays-are-equal-or-not/

QUESTION : Given two arrays A and B of equal size N, the task is to find if given arrays are equal or not. Two arrays are said to be equal if both of them contain same set of elements, arrangements (or permutation) of elements may be different though. Note : If there are repetitions, then counts of repeated elements must also be same for two array to be equal.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(N).

Constraints:
0 <= N <= 10⁷
0 <= A[],B[] <= 10¹⁸

My Solution here

DAY 47: Max distance between same elements.

https://www.geeksforgeeks.org/maximum-distance-two-occurrences-element-array/

QUESTION : Given an array with repeated elements, the task is to find the maximum distance between two occurrences of an element.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(N).

Constraints:
0 <= N <= 10⁶

My Solution here

DAY 48: Two Sum.

https://www.geeksforgeeks.org/given-an-array-a-and-a-number-x-check-for-pair-in-a-with-sum-as-x/

QUESTION : Given an array of positive integers and an integer. Determine whether or not there exist two elements in A whose sum is exactly equal to that integer.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(N).

Constraints:
0 <= N <= 10⁵
1 ≤ A[i] ≤ 10⁵
1 ≤ X ≤ 2*10⁵

My Solution here

DAY 49: Sorting Elements of an Array by Frequency.

https://www.geeksforgeeks.org/sort-elements-by-frequency/

QUESTION : Given an array of integers, sort the array according to frequency of elements. That is elements that have higher frequency come first. If frequencies of two elements are same, then smaller number comes first.

Expected Time Complexity: O(N Log N).
Expected Auxiliary Space: O(N).

Constraints:
0 <= N <= 10⁵
1 ≤ A_i ≤ 10⁵

My Solution here

DAY 50: Print Non-Repeated Elements.

https://www.geeksforgeeks.org/non-repeating-element/

QUESTION : Hashing is very useful to keep track of the frequency of the elements in a list.

You are given an array of integers. You need to print the non-repeated elements as they appear in the array.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(N).

Constraints:
0 <= N <= 10³
1 ≤ Arr_i ≤ 10⁷

My Solution here

DAY 51: Largest subarray with 0 sum.

https://www.geeksforgeeks.org/print-all-subarrays-with-0-sum/

QUESTION : Given an array having both positive and negative integers. The task is to compute the length of the largest subarray with sum 0.

Expected Time Complexity: O(N*Log(N)).
Expected Auxiliary Space: O(N).

Constraints:
0 <= N <= 10⁴
-1000 <= A[i] <= 1000, for each valid i

My Solution here

DAY 52: Top K Frequent Elements in Array - | .

https://www.geeksforgeeks.org/find-k-numbers-occurrences-given-array/

QUESTION : Given a non-empty array of integers, find the top k elements which have the highest frequency in the array. If two numbers have the same frequency then the larger number should be given preference.

Expected Time Complexity: O(N*Log(N)).
Expected Auxiliary Space: O(N).

Constraints:
0 <= N <= 10³
1 <= A[i] <= 10⁴

My Solution here

DAY 53: Sort an array according to the other.

https://www.geeksforgeeks.org/sort-array-according-order-defined-another-array/

QUESTION : Given two integer arrays A1[ ] and A2[ ] of size N and M respectively. Sort the first array A1[ ] such that all the relative positions of the elements in the first array are the same as the elements in the second array A2[ ].

Note: If elements are repeated in the second array, consider their first occurance only.

Expected Time Complexity: O(N*Log(N)).
Expected Auxiliary Space: O(N).

Constraints:
0 <= N, M <= 10⁶
1 <= A1[i], A2[i] <= 10⁶

My Solution here

DAY 54: Zero Sum Subarrays.

https://www.geeksforgeeks.org/find-the-largest-subarray-with-0-sum/

QUESTION : You are given an array arr[] of size n. Find the total count of sub-arrays having their sum equal to 0.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(N).

Constraints:
0 <= N <= 10⁷
10^-10 <= arr[i] <= 10¹⁰

My Solution here

DAY 55: Find All Four Sum Numbers.

https://www.geeksforgeeks.org/find-four-elements-that-sum-to-a-given-value-set-2/

QUESTION : Given an array of integers and another number. Find all the unique quadruple from the given array that sums up to the given number.

Expected Time Complexity: O(N³).
Expected Auxiliary Space: O(N²).

Constraints:
1 <= N <= 100
-1000 <= K <= 1000
-100 <= A[] <= 100

My Solution here

DAY 56: Count distinct elements in every window.

https://www.geeksforgeeks.org/count-distinct-elements-in-every-window-of-size-k/

QUESTION : Given an array of integers and a number K. Find the count of distinct elements in every window of size K in the array.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(N).

Constraints:
1 <= N <= K <= 10⁵
1 <= A[i] <= 10⁵ , for each valid i

My Solution here

DAY 57: Print elememts of a Linkedlist.

QUESTION : Print all elements of a Linked List where we take linked list as input and print the linked list in a single line.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(1).

Constraints:
1 <= N <= 100

My Solution here

DAY 58: Reverse a linked list.

https://www.geeksforgeeks.org/reverse-a-linked-list/

QUESTION : Given a linked list of N nodes. The task is to reverse this list.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(1).

Constraints:
1 <= N <= 100

My Solution here

DAY 59: Occurence of an integer in a Linked List.

https://www.geeksforgeeks.org/write-a-function-that-counts-the-number-of-times-a-given-int-occurs-in-a-linked-list/

QUESTION : Given a singly linked list and a key, count the number of occurrences of given key in the linked list.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(1).

Constraints:
1 <= N <= 10⁴

My Solution here

DAY 60: Pairwise swapping

https://www.geeksforgeeks.org/pairwise-swap-elements-of-a-given-linked-list/

QUESTION : Given a singly linked list of size N. The task is to swap elements in the linked list pairwise.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(1)

Constraints:
1 <= N <= 10³

My Solution here

DAY 61: Add two numbers represented by linked lists.

https://www.geeksforgeeks.org/sum-of-two-linked-lists/

QUESTION : Given two numbers represented by two linked lists of size N and M. The task is to return a sum list. The sum list is a linked list representation of the addition of two input numbers.

Expected Time Complexity: O(N+M)
Expected Auxiliary Space: O(Max(N,M))

Constraints:
1 <= N, M <= 5000

My Solution here

DAY 62: Sorted insert for circular linked list.

https://www.geeksforgeeks.org/sorted-insert-for-circular-linked-list/

QUESTION : Given a sorted circular linked list, the task is to insert a new node in this circular list so that it remains a sorted circular linked list.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(1)

Constraints:
1 <= N <= 10⁵

My Solution here

DAY 63: Split a Circular Linked List into two halves.

https://www.geeksforgeeks.org/split-a-circular-linked-list-into-two-halves/

QUESTION : Given a Cirular Linked List of size N, split it into two halves circular lists. If there are odd number of nodes in the given circular linked list then out of the resulting two halved lists, first list should have one node more than the second list. The resultant lists should also be circular lists and not linear lists.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(1)

Constraints:
1 <= N <= 10²

My Solution here

DAY 64: Reverse a Linked List in groups of given size.

https://www.geeksforgeeks.org/reverse-a-list-in-groups-of-given-size/

QUESTION : Given a linked list of size N. The task is to reverse every k nodes (where k is an input to the function) in the linked list.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(1)

Constraints:
1 <= N <= 10²
1 <= k <= N

My Solution here

DAY 65: Detect Loop in linked list.

https://www.geeksforgeeks.org/detect-loop-in-a-linked-list/

QUESTION : Given a linked list of N nodes. The task is to check if the linked list has a loop. Linked list can contain self loop.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(1)

Constraints:
1 <= N <= 10⁴
1 <= Data on Node <= 10³

My Solution here

DAY 66: Intersection Point in Y Shapped Linked Lists.

https://www.geeksforgeeks.org/write-a-function-to-get-the-intersection-point-of-two-linked-lists/

QUESTION : Given two singly linked lists of size N and M, write a program to get the point where two linked lists intersect each other.

Expected Time Complexity: O(N+M)
Expected Auxiliary Space: O(1)

Constraints:
1 ≤ N + M ≤ 2*10⁵
-1000 ≤ value ≤ 1000

My Solution here

DAY 67: Delete Middle of Linked List.

https://www.geeksforgeeks.org/delete-middle-of-linked-list/

QUESTION : Given a singly linked list, delete middle of the linked list. For example, if given linked list is 1->2->3->4->5 then linked list should be modified to 1->2->4->5.

If there are even nodes, then there would be two middle nodes, we need to delete the second middle element. For example, if given linked list is 1->2->3->4->5->6 then it should be modified to 1->2->3->5->6.

If the input linked list is NULL or has 1 node, then it should return NULL.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(1)

Constraints:
1 <= N <= 1000 1 <= value <= 1000

My Solution here

DAY 68: Clone a linked list with next and random pointer.

https://www.geeksforgeeks.org/a-linked-list-with-next-and-arbit-pointer/

QUESTION : You are given a special linked list with N nodes where each node has a next pointer pointing to its next node. You are also given M random pointers , where you will be given M number of pairs denoting two nodes a and b i.e. a->arb = b.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(1)

Constraints:
1 <= N <= 100 1 <= M <= N 1 <= a, b <= 100

My Solution here

DAY 69: Quick Sort on Linked List.

https://www.geeksforgeeks.org/quicksort-on-singly-linked-list/

QUESTION : Sort the given Linked List using quicksort. which takes O(n^2) time in worst case and O(nLogn) in average and best cases, otherwise you may get TLE.

Constraints:
1<=T<=100 1<=N<=200

My Solution here

DAY 70: Circular Linked List Delete at Position.

https://www.geeksforgeeks.org/delete-middle-of-linked-list/

QUESTION : Given a linked list of size n, you have to delete the node at position pos of the linked list and return the new head. The position of initial node is 1. The tail of the circular linked list is connected to the head using next pointer.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(1)

Constraints:
2 <= number of nodes <= 10³ 1 <= pos <= n

My Solution here

Day 71: QuickSort on Doubly Linked List.

https://www.geeksforgeeks.org/quicksort-for-linked-list/

QUESTION : Sort the given doubly linked list of size N using quicksort. Just complete the partition function using the quicksort technique.

Expected Time Complexity: O(NlogN)
Expected Auxiliary Space: O(1)

Constraints:
1 <= N <= 200

My Solution here

Day 72: Delete without head pointer.

https://www.geeksforgeeks.org/delete-a-node-from-linked-list-without-head-pointer/

QUESTION : You are given a pointer/ reference to the node which is to be deleted from the linked list of N nodes. The task is to delete the node. Pointer/ reference to head node is not given.

Note: No head reference is given to you. It is guaranteed that the node to be deleted is not a tail node in the linked list.

Expected Time Complexity: O(1)
Expected Auxiliary Space: O(1)

Constraints:
1 <= N <= 10³

My Solution here

Day 73: Merge Sort for Doubly Linked List.

https://www.geeksforgeeks.org/merge-sort-for-doubly-linked-list/

QUESTION : Given Pointer/Reference to the head of a doubly linked list of N nodes, the task is to Sort the given doubly linked list using Merge Sort in both non-decreasing and non-increasing order.

Constraints:
1 <= N <= 10⁵

My Solution here

Day 74: Reverse a string using Stack.

https://www.geeksforgeeks.org/stack-set-3-reverse-string-using-stack/

QUESTION : You are given a string S, the task is to reverse the string using stack.

Expected Time Complexity: O(N) Expected Auxiliary Space: O(N)

Constraints:
1 ≤ length of the string ≤ 100

My Solution here

Day 75: Next Greater Element.

https://www.geeksforgeeks.org/next-greater-element-in-same-order-as-input/

QUESTION : Given an array arr[ ] of size N having distinct elements, the task is to find the next greater element for each element of the array in order of their appearance in the array. Next greater element of an element in the array is the nearest element on the right which is greater than the current element. If there does not exist next greater of current element, then next greater element for current element is -1. For example, next greater of the last element is always -1.

Expected Time Complexity: O(N) Expected Auxiliary Space: O(N)

Constraints:
1 ≤ N ≤ 10⁶
1 ≤ Ai ≤ 10¹⁸

My Solution here

Day 76: Get minimum element from stack.

https://www.geeksforgeeks.org/design-a-stack-that-supports-getmin-in-o1-time-and-o1-extra-space/

QUESTION : You are given N elements and your task is to Implement a Stack in which you can get minimum element in O(1) time.

Expected Time Complexity : O(1) for all the 3 methods. Expected Auixilliary Space : O(1) for all the 3 methods.

Constraints:
1 <= Number of queries <= 100
1 <= values of the stack <= 100

My Solution here

Day 77: Evaluation of Postfix Expression.

https://www.geeksforgeeks.org/stack-set-4-evaluation-postfix-expression/#:~:text=The%20expressions%20written%20in%20postfix,are%20not%20required%20in%20postfix.&text=Following%20is%20algorithm%20for%20evaluation,following%20for%20every%20scanned%20element

QUESTION : Given string S representing a postfix expression, the task is to evaluate the expression and find the final value. Operators will only include the basic arithmetic operators like *, /, + and -.

Expected Time Complexity : O(|S|) Expected Auixilliary Space : O(|S|)

Constraints:
1 ≤ |S| ≤ 10⁵

My Solution here

Day 78: Max Rectangle

https://www.geeksforgeeks.org/maximum-size-rectangle-binary-sub-matrix-1s/

QUESTION : Given a binary matrix. Find the maximum area of a rectangle formed only of 1s in the given matrix.

Expected Time Complexity : O(R*C) Expected Auixilliary Space : O(C)

Constraints:
1 <= n,m <= 1000 0 <= M[][] <= 1

My Solution here

Day 79: Sort a stack.

https://www.geeksforgeeks.org/sort-a-stack-using-recursion/

QUESTION : Given a stack, the task is to sort it such that the top of the stack has the greatest element.

Expected Time Complexity : O(N*N) Expected Auixilliary Space : O(N) recursive

Constraints:
1<=N<=100

My Solution here

Day 80: Max area histogram

https://www.geeksforgeeks.org/check-for-balanced-parentheses-in-an-expression/

QUESTION : Find the largest rectangular area possible in a given histogram.

Expected Time Complxity : O(N)
Expected Auxilliary Space : O(N)

Constraints:
1 <= N <= 10^6
1 <= arr[i] <= 10^12

My Solution here

Day 81: Max area histogram

https://www.geeksforgeeks.org/check-for-balanced-parentheses-in-an-expression/

QUESTION : Given an expression string x. Examine whether the pairs and the orders of “{“,”}”,”(“,”)”,”[“,”]” are correct in exp.

For example, the function should return 'true' for exp = “[()]{}{()()}” and 'false' for exp = “[(])”.

Expected Time Complxity : O(|x|)
Expected Auxilliary Space : O(|x|)

Constraints:
1 ≤ |x| ≤ 32000

My Solution here

Day 82: Maximum of minimum for every window size.

https://www.geeksforgeeks.org/find-the-maximum-of-minimums-for-every-window-size-in-a-given-array/

QUESTION : Given an integer array. The task is to find the maximum of the minimum of every window size in the array. Note: Window size varies from 1 to the size of the Array.

Expected Time Complxity : O(N)
Expected Auxilliary Space : O(N)

Constraints:
1 <= N <= 10⁵
1 <= arr[i] <= 10⁵

My Solution here

Day 83: Stock span problem.

https://www.geeksforgeeks.org/the-stock-span-problem/

QUESTION : The stock span problem is a financial problem where we have a series of n daily price quotes for a stock and we need to calculate the span of stock’s price for all n days. The span Si of the stock’s price on a given day i is defined as the maximum number of consecutive days just before the given day, for which the price of the stock on the current day is less than or equal to its price on the given day. For example, if an array of 7 days prices is given as {100, 80, 60, 70, 60, 75, 85}, then the span values for corresponding 7 days are {1, 1, 1, 2, 1, 4, 6}.

Expected Time Complxity : O(N)
Expected Auxilliary Space : O(N)

Constraints:
1 ≤ N ≤ 10⁵
1 ≤ C[i] ≤ 10⁵

My Solution here

Day 84: Infix to Postfix.

https://www.geeksforgeeks.org/stack-set-2-infix-to-postfix/

QUESTION : Given an infix expression in the form of string str. Convert this infix expression to postfix expression. Infix expression: The expression of the form a op b. When an operator is in-between every pair of operands. Postfix expression: The expression of the form a b op. When an operator is followed for every pair of operands. Note: The order of precedence is: ^ greater than * equals to / greater than + equals to -.

Expected Time Complxity : O(|str|)
Expected Auxilliary Space : O(|str|)

Constraints:
1 ≤ |str| ≤ 10⁵

My Solution here

Day 85: Generate Binary Numbers.

https://www.geeksforgeeks.org/interesting-method-generate-binary-numbers-1-n/

QUESTION : Given a number N. The task is to generate and print all binary numbers with decimal values from 1 to N.

Expected Time Complxity : O(N log2N)
Expected Auxilliary Space : O(N log2N)

Constraints:
1 ≤ N ≤ 10⁶

My Solution here

Day 86: Queue Push & Pop.

QUESTION : Given an array arr[] of size N, enqueue the elements of the array into a queue and then dequeue them.

Expected Time Complxity : O(N)
Expected Auxilliary Space : O(N)

Constraints:
1 <= A_i <= 10⁶

My Solution here

Day 87: Queue Push & Pop.

https://www.geeksforgeeks.org/implement-stack-using-queue/

QUESTION : Implement a Stack using two queues q1 and q2.

Expected Time Complxity : O(1) for push() and O(N) for pop()
Expected Auxilliary Space : O(1) for push() and O(N) for pop()

Constraints:
1 <= Number of queries <= 100
1 <= values of the stack <= 100

My Solution here

Day 88: Queue using circular array.

QUESTION : Given size of a queue and Q query. The task is to perform operations according to the type of query. Queries can be of following types: 1) 1 element: This means push the element into the queue (allowed only when queue is not full). 2) 2: This means pop the element at front from the queue (allowed only when queue is not empty).

Constraints:
1 <= size <= 10⁴
1 <= Q <= 10³

My Solution here

DAY 89: Reverse First K elements of Queue.

https://www.geeksforgeeks.org/reversing-first-k-elements-queue/

QUESTION : Given an integer K and a queue of integers, we need to reverse the order of the first K elements of the queue, leaving the other elements in the same relative order.

Only following standard operations are allowed on queue.
enqueue(x) : Add an item x to rear of queue
dequeue() : Remove an item from front of queue
size() : Returns number of elements in queue.
front() : Finds front item.

Expected TIme Complexity : O(n)
Expected Auxilliary Space : O(n)

Constraints:
1 <= N <= 1000
1 <= K <= N

My Solution here

DAY 90: Queue using two Stacks.

https://www.geeksforgeeks.org/queue-using-stacks/

QUESTION : Implement a Queue using 2 stacks s1 and s2 .
A Query Q is of 2 Types
(i) 1 x (a query of this type means pushing 'x' into the queue)
(ii) 2 (a query of this type means to pop element from queue and print the poped element)

Expected TIme Complexity : O(1) for push() and O(N) for pop() or O(N) for push() and O(1) for pop()
Expected Auxilliary Space : O(1)

Constraints:
1 <= Q <= 100
1 <= x <= 100

My Solution here

DAY 91: Maximum of all subarrays of size k.

https://www.geeksforgeeks.org/sliding-window-maximum-maximum-of-all-subarrays-of-size-k/

QUESTION : Given an array arr[] of size N and an integer K. Find the maximum for each and every contiguous subarray of size K.

Expected TIme Complexity : O(N)
Expected Auxilliary Space : O(N)

Constraints:
1 ≤ N ≤ 10⁷
1 ≤ K ≤ N
0 ≤ arr[i] <= 10⁷

My Solution here

DAY 92: Minimum steps to reach target by a Knight.

https://www.geeksforgeeks.org/minimum-steps-reach-target-knight/

QUESTION : Given a square chessboard of N x N size, the position of Knight and position of a target is given. We need to find out the minimum steps a Knight will take to reach the target position.

Expected Time Complexity : O(N²)
Expected Auxilliary Space : O(N²)

Constraints:
1 <= N <= 1000
1 <= Knight_pos(X, Y), Targer_pos(X, Y) <= N

My Solution here

DAY 93: Index of an extra element present in one sorted array.

https://www.geeksforgeeks.org/find-index-of-an-extra-element-present-in-one-sorted-array/

QUESTION : Given two sorted arrays. There is only 1 difference between the arrays. The first array has one element extra added in between. Find the index of the extra element.

Expected Time Complexity : O(log n)
Expected Auxilliary Space : O(1)

Constraints:
1 ≤ N ≤ 10⁷
0 ≤ arr[i] <= 10⁷

My Solution here

DAY 94: Find perimeter of shapes.

https://www.geeksforgeeks.org/find-perimeter-shapes-formed-1s-binary-matrix/

QUESTION : Given a matrix mat[][] of n rows and m columns, consisting of 0’s and 1’s. The task is to complete the function findPerimeter which returns an integer denoting the perimeter of sub-figures consisting of only 1’s in the matrix.

Expected Time Complexity : O(n²)
Expected Auxilliary Space : O(1)

Constraints:
1 <= T <= 100
1 <= n, m <= 20

My Solution here

DAY 95: Count pairs from two linked lists whose sum is equal to a given value.

https://www.geeksforgeeks.org/count-pairs-two-linked-lists-whose-sum-equal-given-value/

QUESTION : Given two linked lists(can be sorted or unsorted) of size n1 and n2 of distinct elements. Given a value x. The problem is to count all pairs from both lists whose sum is equal to the given value x.
Note: The pair has an element from each linked list.

Expected Time Complexity : O(n1 + n2)
Expected Auxilliary Space : O(1)

My Solution here

DAY 96: Check whether the length of given linked list is Even or Odd.

https://www.geeksforgeeks.org/check-whether-the-length-of-given-linked-list-is-even-or-odd/

QUESTION : Given a linked list, task is to make a function which check whether the length of linked list is even or odd.

Expected Time Complexity : O(n)
Expected Auxilliary Space : O(1)

My Solution here

DAY 97: Find the character in first string that is present at minimum index in second string.

https://www.geeksforgeeks.org/find-character-first-string-present-minimum-index-second-string/

QUESTION : Given a string str and another string patt. Find the character in patt that is present at the minimum index in str. If no character of patt is present in str then print ‘No character present’.

Expected Time Complexity : O(max(|str|, |patt|))
Expected Auxilliary Space : O(K) where K <= 26

Constraints:
1 ≤ |str|, |patt| ≤ 10⁴

My Solution here

DAY 98: Count Leaves in Binary Tree.

https://www.geeksforgeeks.org/write-a-c-program-to-get-count-of-leaf-nodes-in-a-binary-tree/

QUESTION : Given a Binary Tree of size N , You have to count leaves in it. For example, there are two leaves in following tree

1
/
10 39
/ 5

Constraints:
1<= N <= 10⁴

My Solution here

Day 99: Right View of Binary Tree.

https://www.geeksforgeeks.org/right-view-binary-tree-using-queue/

QUESTION : Given a Binary Tree, find Right view of it. Right view of a Binary Tree is set of nodes visible when tree is viewed from right side.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(Height of the Tree).

Constraints:
1 <= Number of nodes <= 10⁵
1 <= Data of a node <= 10⁵

My Solution here

Day 100: Two Mirror Trees.

https://www.geeksforgeeks.org/check-if-two-trees-are-mirror/

QUESTION : Given a Two Binary Trees, write a function that returns true if one is mirror of other, else returns false.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(Height of the Tree).

Constraints:
1 <= Number of nodes<= 10000
-1000 <= Data of a node<= 1000

My Solution here

Day 101: Diameter of Binary Tree.

https://www.geeksforgeeks.org/diameter-of-a-binary-tree/

QUESTION : Given a Binary Tree, find diameter of it. The diameter of a tree is the number of nodes on the longest path between two end nodes in the tree.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(Height of the Tree).

Constraints:
1 <= Number of nodes<= 10000
1 <= Data of a node<= 1000

My Solution here

Day 102: Sum Tree .

https://www.geeksforgeeks.org/check-if-a-given-binary-tree-is-sumtree/

QUESTION : Given a Binary Tree. Check whether it is a Sum Tree or not. A Binary Tree is a Sum Tree in which value of each node x is equal to sum of nodes present in its left subtree and right subtree . An empty tree is also a Sum Tree as sum of an empty tree can be considered to be 0. A leaf node is also considered as a Sum Tree.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(Height of the Tree).

Constraints:
1 ≤ number of nodes ≤ 10⁴

My Solution here

Day 103: ZigZag Tree Traversal.

https://www.geeksforgeeks.org/level-order-traversal-in-spiral-form/

QUESTION : Given a Binary Tree. Find the Zig-Zag Level Order Traversal of the Binary Tree.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(N).

Constraints:
1 ≤ number of nodes ≤ 10⁴

My Solution here

Day 104: Level Order Traversal.

https://www.geeksforgeeks.org/level-order-traversal-in-spiral-form/

QUESTION : Complete the function to find spiral order traversal of a tree.

Expected Time Complexity: O(N).
Expected Auxiliary Space: O(N).

Constraints:
0 <= Number of nodes <= 10⁵
0 <= Data of a node <= 10⁵

My Solution here

Day 105

Day 106: Determine if Two Trees are Identical .

https://www.geeksforgeeks.org/write-c-code-to-determine-if-two-trees-are-identical/

QUESTION : Given two binary trees, the task is to find if both of them are identical or not.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(height of tree)

Constraints: 1 <= Number of nodes <= 10⁵
1 <= Data of a node <= 10⁵

My Solution here

Day 107: Root to leaf path sum.

https://www.geeksforgeeks.org/root-to-leaf-path-sum-equal-to-a-given-number/

QUESTION : Given a binary tree and an integer S, check whether there is root to leaf path with its sum as S.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(height of tree)

Constraints: 1 ≤ N ≤ 10⁴
1 ≤ S ≤ 10⁶

My Solution here

Day 108: Vertical sum.

https://www.geeksforgeeks.org/vertical-sum-in-a-given-binary-tree/

QUESTION : Given a Binary Tree, find vertical sum of the nodes that are in same vertical line. Print all sums through different vertical lines starting from left-most vertical line to right-most vertical line.

Expected Time Complexity: O(N)
Expected Auxiliary Space: O(N)

Constraints: 1 <= Number of nodes <= 1000

My Solution here