Solution: Permutations

---

examples/permutations/permutations.go

package main

import (
    "fmt"
)

func main() {
    results := permutations("a")
    fmt.Println(results)
}

// We assume they are unique
func permutations(word string) []string {
    if word == "" {
        return []string{""}
    }
    perms := []string{}
    for i, rn := range word {
        rest := word[:i] + word[i+1:]
        //fmt.Println(rest)
        for _, result := range permutations(rest) {
            perms = append(perms, fmt.Sprintf("%c", rn)+result)
        }
        //perms = append(perms, fmt.Sprintf("%c\n", rn))
    }
    return perms
}

examples/permutations/permutations_test.go

package main

import (
    "fmt"
    "sort"
    "testing"
)

func TestPermutations(t *testing.T) {
    cases := make(map[string][]string)
    cases["a"] = []string{"a"}
    cases["ab"] = []string{"ab", "ba"}
    cases["abc"] = []string{"abc", "acb", "bac", "bca", "cab", "cba"}
    cases["abcd"] = []string{
        "dabc", "dacb", "dbac", "dbca", "dcab", "dcba",
        "adbc", "adcb", "bdac", "bdca", "cdab", "cdba",
        "abdc", "acdb", "badc", "bcda", "cadb", "cbda",
        "abcd", "acbd", "bacd", "bcad", "cabd", "cbad"}

    for inp, expected := range cases {
        actual := permutations(inp)
        if !compare(expected, actual) {
            t.Error(fmt.Sprintf("Expected '%v', Actual '%v'", expected, actual))
        }
    }
}

func compare(a, b []string) bool {
    //fmt.Println(a)
    //fmt.Println(b)
    if len(a) != len(b) {
        return false
    }
    sort.Strings(a)
    sort.Strings(b)

    for i := 0; i < len(a); i++ {
        if a[i] != b[i] {
            return false
        }
    }
    return true
}