23: non-abundant sums

23_non_abundant_sums/abundant_test.go

@@ -0,0 +1,82 @@
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func Test_isAbundantNumber(t *testing.T) {
+	tt := []struct {
+		name  string
+		input int
+		want  bool
+	}{
+		{
+			"1",
+			1,
+			false,
+		},
+		{
+			"12",
+			12,
+			true,
+		},
+		{
+			"28",
+			28,
+			false,
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			got := isAbundantNumber(tc.input)
+			if got != tc.want {
+				t.Errorf("isAbundantNumber() = %v, want %v", got, tc.want)
+			}
+		})
+	}
+}
+
+func Test_sumOfDivisors(t *testing.T) {
+	tt := []struct {
+		name  string
+		input int
+		want  int
+	}{
+		{
+			"1",
+			1,
+			0,
+		},
+		{
+			"2",
+			2,
+			1,
+		},
+		{
+			"4",
+			4,
+			3,
+		},
+		{
+			"12",
+			12,
+			16,
+		},
+		{
+			"28",
+			28,
+			28,
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			got := sumOfDivisors(tc.input)
+			if !reflect.DeepEqual(got, tc.want) {
+				t.Errorf("sumOfDivisors() = %d, want %d", got, tc.want)
+			}
+		})
+	}
+}

23_non_abundant_sums/main.go

@@ -0,0 +1,55 @@
+package main
+
+import "fmt"
+
+func main() {
+	sum := 0
+	var nums []int
+	ans := make(map[int]struct{})
+	for i := 1; i < 28123; i++ {
+		if isAbundantNumber(i) {
+			ans[i] = struct{}{}
+		}
+		find := false
+		for k := range ans {
+			d := i - k
+			if d < 0 {
+				break
+			}
+			if _, f := ans[d]; f {
+				fmt.Printf("%d = %d + %d\n", i, k, d)
+				find = true
+				break
+			}
+		}
+		if !find {
+			sum += i
+			nums = append(nums, i)
+		}
+	}
+	fmt.Println("abundant numbers:", ans)
+	fmt.Println("sum:", sum, "nums:", nums)
+}
+
+func isAbundantNumber(input int) bool {
+	return sumOfDivisors(input) > input
+}
+
+func sumOfDivisors(input int) int {
+	if input < 2 {
+		return 0
+	}
+	sum := 0
+	i := 1
+	for i*i <= input {
+		if input%i == 0 {
+			sum += i
+			j := input / i
+			if j != i && j != input {
+				sum += j
+			}
+		}
+		i++
+	}
+	return sum
+}