Solution to the latest cassidoo challenge

antidivisor.go

package main

import (
	"fmt"
	"os"
	"strconv"
)

func main() {
	if len(os.Args) == 1 {
		fmt.Println("Missing input integer.")
		os.Exit(1)
	}

	n, err := strconv.Atoi(os.Args[1])
	if err != nil {
		fmt.Println("Input must be integer.")
		os.Exit(1)
	}

	fmt.Println(antidivisors(n))
}

func antidivisors(n int) []int {
	advs := []int{}
	for k := 2; k < n; k++ {
		if k%2 == 0 && n%k == k/2 {
			advs = append(advs, k)
		} else if k%2 != 0 && (n%k == (k-1)/2 || n%k == (k+1)/2) {
			advs = append(advs, k)
		}
	}

	return advs
}

antidivisor_test.go

package main

import (
	"fmt"
	"testing"
)

func TestAntidivisor(t *testing.T) {
	cases := []struct {
		input    int
		expected []int
	}{
		{2, []int{}},
		{3, []int{2}},
		{4, []int{3}},
		{5, []int{2, 3}},
		{6, []int{4}},
		{13, []int{2, 3, 5, 9}},
		{38, []int{3, 4, 5, 7, 11, 15, 25}},
	}

	for _, tc := range cases {
		t.Run(fmt.Sprintf("%d", tc.input), func(t *testing.T) {
			actual := antidivisors(tc.input)
			if len(tc.expected) != len(actual) {
				fmt.Printf("expected:\t%+v\nactual:\t\t%+v\n", tc.expected, actual)
				t.Fatal()
			}
			for i, expected := range tc.expected {
				if expected != actual[i] {
					fmt.Printf("expected:\t%+v\nactual:\t\t%+v\n", tc.expected, actual)
					t.Fail()
				}
			}
		})
	}
}