Description
Given a collection of numbers that might contain duplicates, return all possible unique permutations.
Example
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| Input: [1,1,2]
Output:
[
[1,1,2],
[1,2,1],
[2,1,1]
]
|
Solution
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| class Solution {
public List<List<Integer>> permuteUnique(int[] nums) {
List<List<Integer>> res = new ArrayList<>();
if (nums == null || nums.length == 0) return res;
Arrays.sort(nums);
boolean[] visited = new boolean[nums.length];
helper(nums, res, new ArrayList<>(), visited);
return res;
}
private void helper(int[] nums, List<List<Integer>> res, List<Integer> cur, boolean[] visited){
if (cur.size() == nums.length){
res.add(new ArrayList<>(cur));
return;
}
for (int i = 0; i < nums.length; i++){
if (visited[i]) continue;
if (i > 0 && nums[i] == nums[i - 1] && !visited[i - 1]) continue;
cur.add(nums[i]);
visited[i] = true;
helper(nums, res, cur, visited);
visited[i] = false;
cur.remove(cur.size() - 1);
}
}
}
|