package top100liked

import (
	"fmt"
	"testing"
)

// https://leetcode.cn/problems/permutations?envType=study-plan-v2&envId=top-100-liked

func permute(nums []int) [][]int {
	l := len(nums)
	fact := 1
	for i := 2; i <= l; i++ {
		fact *= i
	}
	res := make([][]int, 0, fact)
	var helper func(nums []int, used []bool, r []int)
	helper = func(nums []int, used []bool, r []int) {
		for i, v := range used {
			if !v {
				used[i] = true
				r = append(r, nums[i])
				if len(r) == l {
					cp := make([]int, l)
					copy(cp, r)
					res = append(res, cp)
				} else {
					helper(nums, used, r)
				}
				r = r[:len(r)-1]
				used[i] = false
			}
		}
	}
	helper(nums, make([]bool, l), make([]int, 0))
	return res
}

func Test(t *testing.T) {
	fmt.Printf("%+v", permute([]int{5, 4, 6, 2}))
}