Goで順列を辞書順で - 電波ビーチ

スライスのポインタで渡すところとスライスのコピーとスライスの任意のインデックスの要素を消すっていう実装が頭まわりませんでした…

実装

package main
import "fmt"

func main(){
    test := []int{1, 2, 3, 4}
    perms := permuration(test, 3)
    fmt.Println("1から4の中から3つ取る順列")
    fmt.Println(perms)

    // int以外の場合でもどうせインデックスを返すので数列を渡せばいい
    aquars := []string{"千歌", "梨子", "曜", "ダイヤ", "果南", "鞠莉", "善子", "花丸", "ルビィ"}
    indices := make([]int, len(aquars))
    for i := 0; i<len(aquars); i++{
        indices[i] = i
    }
    coupling := permuration(indices,  3)
    for _, c := range coupling{
        for i, v := range c{
            fmt.Print(aquars[v])
            if i<2{
                fmt.Print(" x ")
            }
        }
        fmt.Println()
    }
}

func permuration(target []int, limit int)([][]int){
    if limit<1 || len(target)<limit{
        return nil
    }
    ret := make([][]int, 0)
    gen_perm(make([]int, 0), target, &ret, limit)
    return ret
}

func gen_perm(perm []int, rest []int, lis *[][]int, n int){
    if n==0{
        *lis = append(*lis, perm)
    }else{
        // 探索
        for i, r := range rest{
            next_rest := make([]int, 0)
            next_rest = append(next_rest, rest...)
            next_perm := make([]int, 0)
            next_perm = append(next_perm, perm...)

            next_rest = deleteIndex(next_rest, i)
            next_perm = append(next_perm, r)
            gen_perm(next_perm, next_rest, lis, n-1)
        }

    }
}

func deleteIndex(in []int, index int)[]int{
    out := make([]int, 0)
    out = append(out, in...)
    if index<0 || len(in)<index{
        fmt.Println("delete index mis")
        return nil
    }
    out = append(out[:index], out[index+1:]...)
    return out
}