46. Permutations

Question

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 2:

Input: nums = [1]
Output: [[1]]

Constraints:

• 1 <= nums.length <= 6
• -10 <= nums[i] <= 10
• All the integers of nums are unique.

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Approach

Solution

class Solution {
public:
    vector<vector<int>> out;
    
    vector<vector<int>> permute(vector<int>& nums) {
        dfs(0,nums);
        return out;
    }
    
    void dfs(int i, vector<int>& nums){
        if (i == nums.size()){
            out.push_back(nums);
            return;
        }
        
        for(int j = i; j < nums.size(); j++){
            int tmp = nums[i];
            nums[i] = nums[j];
            nums[j] = tmp;
            
            dfs(i+1,nums);
            
            tmp = nums[i];
            nums[i] = nums[j];
            nums[j] = tmp;
        }
    }
};