feat: add perfectnumber (#554)

math/perfectnumber.go

@@ -0,0 +1,36 @@
+// perfectnumber.go
+// description: provides the function IsPerfectNumber and related utilities
+// details:
+// provides the functions
+// - IsPerfectNumber which checks if the input is a perfect number,
+// - SumOfProperDivisors which returns the sum of proper divisors of the input.
+// A number is called perfect, if it is a sum of its proper divisors,
+// cf. https://en.wikipedia.org/wiki/Perfect_number,
+// https://mathworld.wolfram.com/PerfectNumber.html
+// https://oeis.org/A000396
+// author(s) [Piotr Idzik](https://github.com/vil02)
+// see perfectnumber_test.go
+
+package math
+
+// Returns the sum of proper divisors of inNumber.
+func SumOfProperDivisors(inNumber uint) uint {
+	var res = uint(0)
+	if inNumber > 1 {
+		res = uint(1)
+	}
+	for curDivisor := uint(2); curDivisor*curDivisor <= inNumber; curDivisor++ {
+		if inNumber%curDivisor == 0 {
+			res += curDivisor
+			if curDivisor*curDivisor != inNumber {
+				res += inNumber / curDivisor
+			}
+		}
+	}
+	return res
+}
+
+// Checks if inNumber is a perfect number
+func IsPerfectNumber(inNumber uint) bool {
+	return inNumber > 0 && SumOfProperDivisors(inNumber) == inNumber
+}

math/perfectnumber_test.go

@@ -0,0 +1,151 @@
+package math_test
+
+import (
+	"testing"
+
+	"github.com/TheAlgorithms/Go/math"
+)
+
+type testCaseSumOfProperDivisors struct {
+	input    uint
+	expected uint
+}
+
+// getSumOfProperDivisorsTestCases returns an array of test data
+// for the tests of the function SumOfProperDivisors.
+// Data was verified using [A001065].
+// [A001065]: https://oeis.org/A001065/b001065.txt
+func getSumOfProperDivisorsTestCases() []testCaseSumOfProperDivisors {
+	return []testCaseSumOfProperDivisors{
+		{0, 0},
+		{1, 0},
+		{2, 1},
+		{3, 1},
+		{4, 3},
+		{5, 1},
+		{6, 6},
+		{7, 1},
+		{8, 7},
+		{9, 4},
+		{10, 8},
+		{11, 1},
+		{12, 16},
+		{13, 1},
+		{14, 10},
+		{15, 9},
+		{16, 15},
+		{17, 1},
+		{18, 21},
+		{19, 1},
+		{20, 22},
+		{21, 11},
+		{22, 14},
+		{23, 1},
+		{24, 36},
+		{25, 6},
+		{26, 16},
+		{27, 13},
+		{28, 28},
+		{29, 1},
+		{30, 42},
+		{31, 1},
+		{32, 31},
+		{33, 15},
+		{34, 20},
+		{35, 13},
+		{36, 55},
+		{37, 1},
+		{38, 22},
+		{39, 17},
+		{40, 50},
+		{41, 1},
+		{42, 54},
+		{43, 1},
+		{44, 40},
+		{45, 33},
+		{46, 26},
+		{47, 1},
+		{48, 76},
+		{49, 8},
+		{50, 43},
+		{51, 21},
+		{52, 46},
+		{53, 1},
+		{54, 66},
+		{55, 17},
+		{56, 64},
+		{57, 23},
+		{58, 32},
+		{59, 1},
+		{60, 108},
+		{800, 1153},
+		{8204, 8260},
+		{9646, 8498},
+		{9756, 14996},
+		{9829, 1},
+		{9954, 15006},
+		{10000, 14211},
+	}
+}
+
+func TestSumOfProperDivisors(t *testing.T) {
+	for _, tc := range getSumOfProperDivisorsTestCases() {
+		actual := math.SumOfProperDivisors(tc.input)
+		if actual != tc.expected {
+			t.Errorf(
+				"Expected SumOfProperDivisors(%d) to be: %d, but got: %d",
+				tc.input, tc.expected, actual)
+		}
+	}
+}
+
+func BenchmarkSumOfProperDivisors(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		math.SumOfProperDivisors(800)
+	}
+}
+
+type isPerfectNumberTestCase struct {
+	number    uint
+	isPerfect bool
+}
+
+// getIsPerfectNumberTestCases returns an array of test data
+// for the tests of the function IsPerfectNumber
+// Data was verified using [A000396].
+// [A000396]: https://oeis.org/A000396
+func getIsPerfectNumberTestCases() []isPerfectNumberTestCase {
+	return []isPerfectNumberTestCase{
+		{6, true},
+		{28, true},
+		{496, true},
+		{8128, true},
+		{33550336, true},
+		{0, false},
+		{1, false},
+		{2, false},
+		{3, false},
+		{4, false},
+		{5, false},
+		{7, false},
+		{100, false},
+		{219, false},
+		{997, false},
+		{33550335, false},
+		{33550337, false},
+	}
+}
+
+func TestIsPerfectNumber(t *testing.T) {
+	for _, tc := range getIsPerfectNumberTestCases() {
+		if math.IsPerfectNumber(tc.number) != tc.isPerfect {
+			t.Errorf("Unexpected output for %d", tc.number)
+		}
+	}
+}
+
+func BenchmarkIsPerfectNumber(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		math.IsPerfectNumber(8128)
+	}
+}