Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.
Examples
Input: nums = [1,2,3] Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
Input: nums = [0,1] Output: [[0,1],[1,0]]
Input: nums = [1] Output: [[1]]
Constraints:
1 <= nums.length <= 6 -10 <= nums[i] <= 10 All the integers of nums are unique.
Java Solution (Backtracking)
class Solution {
public List<List<Integer>> permute(int[] nums) {
List<List<Integer>> perms = new ArrayList<>();
permuteHelper(perms, new ArrayList<>(), nums);
return perms;
}
private void permuteHelper(List<List<Integer>> perms, List<Integer> tempList, int[] nums) {
if(tempList.size() == nums.length){
perms.add(new ArrayList<>(tempList));
} else{
for(int i = 0; i < nums.length; i++) {
if(tempList.contains(nums[i])) continue; // element already exists, skip
tempList.add(nums[i]);
permuteHelper(perms, tempList, nums);
tempList.remove(tempList.size() - 1);
}
}
}
}