Permutations Problem


Description

LeetCode Problem 46.

Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.

Example 1:

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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:

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Input: nums = [0,1]
Output: [[0,1],[1,0]]

Example 3:

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

Constraints:

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


Sample C++ Code

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




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