public class Solution {
public List<List> permuteUnique(int[] nums) {
List<List> res = new ArrayList<List>();
Set<List> set = new HashSet<List>();
helper(nums, res, set, 0);
return res;
}
private void helper(int[] nums, List<List<Integer>> res, Set<List<Integer>> set, int index) {
if(index == nums.length) {
List<Integer> list = new ArrayList<Integer>();
for(int i : nums)
list.add(i);
if(!set.contains(list)) {
set.add(list);
res.add(list);
}
}
for(int i = index; i < nums.length; i++) {
swap(nums, index, i);
helper(nums, res, set, index+1);
//使得数组的顺序可以恢复成交换前的顺序，能够满足所有的情况
swap(nums, i, index);
}
}
private void swap(int[] nums, int i, int j) {
int temp = nums[i];
nums[i] = nums[j];
nums[j] = temp;
}
Shawngbk
commented
7 years ago
public class Solution { public List<List> permuteUnique(int[] nums) {
List<List> res = new ArrayList<List>();
Set<List> set = new HashSet<List>();
helper(nums, res, set, 0);
return res;
}
}