Get all permutations of a set of strings

permute.go

func permute(opts []string) []string {
        return _permute("", opts)
}

func _permute(s string, opts []string) []string {
	if len(opts) == 0 {
		return []string{s}
	}
	ret := make([]string, 0, 16)
	olist := make([]string, 0, len(opts))
	for i := 0; i < len(opts); i++ {
		a := s + opts[i]
		olist = olist[:0]
		for j := 0; j < len(opts); j++ {
			if j != i {
				olist = append(olist, opts[j])
			}
		}
		ret = append(ret, _permute(a, olist)...)
	}
	return ret
}