Recursion_Permutations.cpp

https://leetcode.com/problems/permutations/

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 nums are unique.



class Solution {
public:
    vector<vector<int>> permute(vector<int>& nums) {

        vector<vector<int>> ans;

        PermuteRec(nums, 0, ans);

        return ans;
        
    }

    vector<vector<int>> PermuteRec(vector<int>& nums, int idx, vector<vector<int>> &ans)
    {
        if (idx == nums.size())
        {
            ans.push_back(nums);
            return ans;
        }

        for(int i = idx; i < nums.size(); ++i)
        {
            swap(nums[i], nums[idx]);
            PermuteRec(nums, idx+1, ans);
            swap(nums[i], nums[idx]);
        }

        return ans;

    }
    
};