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