Permutations II

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Given a list of numbers with duplicate number in it. Find all unique permutations.

class Solution {    /**     * @param nums: A list of integers.     * @return: A list of unique permutations.     */    public List<List<Integer>> permuteUnique(int[] nums) {        List<List<Integer>> results = new ArrayList<>();        if (nums == null) {            return results;        }        if (nums.length == 0) {            results.add(new ArrayList<Integer>());            return results;        }        List<Integer> result = new ArrayList<>();        Set<List<Integer>> hash = new HashSet<>();        int[] visited = new int[nums.length];        dfsHelper(nums, visited, results, result, hash);        return results;    }    private void dfsHelper(int[] nums,                           int[] visited,                           List<List<Integer>> results,                           List<Integer> result,                           Set<List<Integer>> hash) {        if (result.size() == nums.length ) {            List<Integer> temp = new ArrayList<Integer>(result);            if (!hash.contains(temp)) {                results.add(temp);                hash.add(temp);            }        }        for (int i = 0; i < nums.length; i++) {            if (visited[i] == 1) {                continue;            }            result.add(nums[i]);            visited[i] = 1;            dfsHelper(nums, visited, results, result, hash);            result.remove(result.size() - 1);            visited[i] = 0;        }    }}

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