47. 全排列 II

给定一个可包含重复数字的序列，返回所有不重复的全排列。

示例:

输入: [1,1,2]
输出:
[
[1,1,2],
[1,2,1],
[2,1,1]
]

 

class Solution:
    def permuteUnique(self, nums: List[int]) -> List[List[int]]:
        return list(set(itertools.permutations(nums)))

 

class Solution {
    public List<List<Integer>> permuteUnique(int[] nums) {
        List<List<Integer>> list = new ArrayList<>();
        Arrays.sort(nums);
        backtrack(list, new ArrayList<>(), nums, new boolean[nums.length]);
        return list;
    }

    private void backtrack(List<List<Integer>> list, List<Integer> tempList, int [] nums, boolean [] used){
        if(tempList.size() == nums.length){
            list.add(new ArrayList<>(tempList));
        } else{
            for(int i = 0; i < nums.length; i++){
                if(used[i] || i > 0 && nums[i] == nums[i-1] && !used[i - 1]) continue;
                used[i] = true; 
                tempList.add(nums[i]);
                backtrack(list, tempList, nums, used);
                used[i] = false; 
                tempList.remove(tempList.size() - 1);
            }
        }
    }
}