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PermuteUnique47.java
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PermuteUnique47.java
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package Leetcode;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class PermuteUnique47 {
/*Method: BackTrack, Time: O(N*N!), Space:O(N)**/
List<List<Integer>> res = new ArrayList<>();
List<Integer> list = new ArrayList<>();
public List<List<Integer>> permuteUnique(int[] nums) {
boolean[] visited = new boolean[nums.length];
Arrays.sort(nums);
backtrack(nums, 0, visited);
return res;
}
private void backtrack(int[] nums, int begin, boolean[] visited) {
if(begin == nums.length) {
res.add(new ArrayList<>(list));
return;
}
for(int i=0; i< nums.length; i++) {
if(visited[i] || (i>0 && nums[i] == nums[i-1] && !visited[i-1])) {
continue;
}
visited[i] = true;
list.add(nums[i]);
backtrack(nums, begin + 1, visited);
visited[i] = false;
list.remove(list.size() - 1);
}
}
}