384 Shuffle an Array

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();

Solution

class Solution {
public:
    vector<int> original;
    Solution(vector<int> nums) {
        original = nums;
    }

    /** Resets the array to its original configuration and return it. */
    vector<int> reset() {
        return original;
    }

    /** Returns a random shuffling of the array. */
    vector<int> shuffle() {
        int n = original.size();
        vector<int> res = original;
        for ( int i = n-1; i >= 0; i-- ) {
            int j = rand()%(i+1);
            swap(res[i], res[j]);
        }
        return res;
    }
};

/**
 * 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();
 */