多了一步去重。
class Solution {
public List<List<Integer>> permuteUnique(int[] nums) {
int len = nums.length;
List<List<Integer>> res = new ArrayList<>();
if (len == 0) return res;
Arrays.sort(nums);
Deque<Integer> path = new ArrayDeque<>();
boolean[] used = new boolean[len];
_dfs(nums, len, 0, path, used, res);
return res;
}
private void _dfs(int[] nums, int len, int depth, Deque<Integer> path
, boolean[] used, List<List<Integer>> res) {
if (depth == len) {
res.add(new ArrayList<>(path));
return;
}
for (int i = 0; i < len; i++) {
if (used[i]) continue;
if (i > 0 && nums[i] == nums[i-1] && !used[i-1]) continue;
path.addLast(nums[i]);
used[i] = true;
_dfs(nums, len, depth + 1, path, used, res);
//回朔
path.removeLast();
used[i] = false;
}
}
}