Golang有重复字符串的排列组合

package main

import "fmt"

func permutation(S string) []string {
    m := make(map[string]bool)
    m[S] = true
    l := len(S)
    for i := 0; i < l-1; i ++ {
        for j := i + 1; j < l; j ++ {
            for s, _ := range m {
                t := []byte(s)
                t[i], t[j] = t[j], t[i]
                m[string(t)] = true
            }
        }
    }
    ret := make([]string, len(m))
    i := 0
    for s, _ := range m {
        ret[i] = s
        i ++
    }
    return ret
}

func main()  {
	fmt.Println(permutation("1223"))
}

输出
[1223 2213 3212 2321 1232 2231 2123 3221 3122 1322 2312 2132]