LeetCode-in-All
46. Permutations
Medium
Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.
Example 1:
Input: nums = [1,2,3]
Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
Example 2:
Input: nums = [0,1]
Output: [[0,1],[1,0]]
Example 3:
Input: nums = [1]
Output: [[1]]
Constraints:
1 <= nums.length <= 6-10 <= nums[i] <= 10- All the integers of
numsare unique.
Solution
class Solution {
List<List<int>> permute(List<int> nums) {
List<List<int>> ans = [];
List<bool> used = List<bool>.filled(nums.length, false);
helper(ans, [], used, nums);
return ans;
}
void helper(List<List<int>> ans, List<int> temp, List<bool> used, List<int> nums) {
if (temp.length == nums.length) {
ans.add(List<int>.from(temp));
return;
}
for (int i = 0; i < nums.length; i++) {
if (used[i]) continue;
temp.add(nums[i]);
used[i] = true;
helper(ans, temp, used, nums);
temp.removeLast();
used[i] = false;
}
}
}