[Leetcode] Permutations II (Java)

来源：互联网发布：搜索引擎和大数据编辑：程序博客网时间：2024/05/16 06:56

Given a collection of numbers that might contain duplicates, return all possible unique permutations.

For example,
[1,1,2] have the following unique permutations:
[1,1,2], [1,2,1], and [2,1,1].

数组中存在重复，不输出重复解

先对原数组排序，然后根据顺序比如[1,1,2]，若第一个1未进入，则第二个1不能进入，要按顺序来，加上标志位flag即可

public class Solution {     public ArrayList<ArrayList<Integer>> permuteUnique(int[] num) {    ArrayList<ArrayList<Integer>> res = new ArrayList<ArrayList<Integer>>();ArrayList<Integer> list = new ArrayList<Integer>();Arrays.sort(num);boolean[] flag = new boolean[num.length];dfs(num,0,res,list,flag);return res;    }private void dfs(int[] num,int index, ArrayList<ArrayList<Integer>> res, ArrayList<Integer> list, boolean[] flag){if(index==num.length){res.add(new ArrayList<Integer>(list));return;}for(int i=0;i<num.length;i++){if(flag[i]||(i>0&&num[i-1]==num[i]&&!flag[i-1]))continue;list.add(num[i]);flag[i]=true;dfs(num, index+1, res,list,flag);list.remove(list.size()-1);flag[i]=false;}}}

0 0