# 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:

``````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:

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

Example 3:

``````1
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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;
}
};
``````