LC 384. Shuffle an Array

Posted 2021-01-30 ethanhong

 

Shuffle a set of numbers without duplicates.

Example:

// Init an array with set 1, 2, and 3.
int[] nums = {1,2,3};
Solution solution = new Solution(nums);

// Shuffle the array [1,2,3] and return its result. Any permutation of [1,2,3] must equally likely to be returned.
solution.shuffle();

// Resets the array back to its original configuration [1,2,3].
solution.reset();

// Returns the random shuffling of array [1,2,3].
solution.shuffle();

 

Runtime: 244 ms, faster than 36.91% of C++ online submissions for Shuffle an Array.

 

class Solution {
private:
  vector<int> Nums ;
public:
    Solution(vector<int> nums) {
        Nums = nums;
    }
    
    /** Resets the array to its original configuration and return it. */
    vector<int> reset() {
      return Nums;
    }
    
    /** Returns a random shuffling of the array. */
    vector<int> shuffle() {
      vector<int> tmpnums = Nums;
      for(int i=0; i<Nums.size(); i++){
        int newidx = i + rand()%(Nums.size() - i);
        int tmp = tmpnums[i];
        tmpnums[i] = tmpnums[newidx];
        tmpnums[newidx] = tmp;
      }
      return tmpnums;
    }
};

/**
 * Your Solution object will be instantiated and called as such:
 * Solution obj = new Solution(nums);
 * vector<int> param_1 = obj.reset();
 * vector<int> param_2 = obj.shuffle();
 */