number_complement.c

/* Given a positive integer, output its complement number. 
 * The complement strategy is to flip the bits of its binary representation.
 *
 * Note:
 * The given integer is guaranteed to fit within the range of a 32-bit signed integer.
 * You could assume no leading zero bit in the integer’s binary representation.
 *
 * Example 1:
 * Input: 5
 * Output: 2
 * Explanation: The binary representation of 5 is 101 (no leading zero bits), 
 * and its complement is 010. So you need to output 2.
 *
 * Example 2:
 * Input: 1
 * Output: 0
 * Explanation: The binary representation of 1 is 1 (no leading zero bits), 
 * and its complement is 0. So you need to output 0.
 */

#include <stdio.h>
#include <math.h>

int findComplement(int);

int main()
{
    int num;
    printf("Enter a number:");
    scanf("%d", &num);
    int number_complement = findComplement(num);
    printf("Number Complement:%d\n", number_complement);
    return 0;
}

int findComplement(int num)
{
    return ~num & (1 << ((int)log2(num)+ 1)) - 1;
}