Permutations

Posted by Bill on October 31, 2023

Permutations

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

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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]]

Solution

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class Solution {
  private:
  set<vector<int>> mySet;
  void permuteImpl(vector<int>& nums, int begin, int len) {
    if (begin == len) {
      return;
    }
    for (int i = begin; i < len; i++) {
      swap(nums[begin], nums[i]);
      mySet.insert(nums);
      permuteImpl(nums, begin + 1, len);
      swap(nums[begin], nums[i]);
    }
  }

  public:
  vector<vector<int>> permute(vector<int>& nums) {
    int len = nums.size();
    permuteImpl(nums, 0, len);
    vector<vector<int>> ans;
    for (auto item : mySet) {
      ans.push_back(item);
    }
    return ans;
  }
};