[leetcode-47]Permutations II(java)

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问题描述：
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].

分析：如leetcode-46，代码丝毫未变。
代码如下：356ms

public class Solution {    public List<List<Integer>> permuteUnique(int[] nums){        List<List<Integer>> res = new LinkedList<>();        List<Integer> tmpList = new LinkedList<>();        boolean[] visited = new boolean[nums.length];        Arrays.sort(nums);        solve(nums, res, tmpList,visited);        return res;    }    private void solve(int[] nums,List<List<Integer>> res,List<Integer> tmpList,boolean[] visited){        int length = nums.length;        if(tmpList.size()==length){            res.add(new LinkedList<>(tmpList));            return;        }        for(int i = 0;i<length;i++){            while(i>0&&i<length&&nums[i]==nums[i-1]&&!visited[i-1]) i++;            if(i==length)                return;            if(visited[i]) continue;            tmpList.add(nums[i]);            visited[i] = true;            solve(nums,res,tmpList,visited);            visited[i] = false;            tmpList.remove(tmpList.size()-1);        }    }}

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