题目描述
Given a collection of numbers that might contain duplicates, return all possible unique permutations.
样例
Example:
Input: [1,1,2] Output: [ [1,1,2], [1,2,1], [2,1,1] ]
思路分析
思路和上题基本一致,不过此题增加了重复元素,需要添加边界判断条件
代码
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); } } }
结果
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