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> v;
    int size;
    Solution(vector<int> nums) {
        v = nums;
        size = nums.size();
        srand(time(0));
    }
    
    /** Resets the array to its original configuration and return it. */
    vector<int> reset() {
        return v;
    }
    
    /** Returns a random shuffling of the array. */
    vector<int> shuffle() {
        vector<int> t(v);
        for(int i=0;i<size - 1;i++){
            int r = randomBetween(i, size-1);
            swap(t[i], t[r]);
        }
        return t;
    }
    
    inline void swap(int &a, int &b){
        int t = a;
        a = b;
        b = t;
    }
    
    int randomBetween(int a, int b){
        if(a == b) return a;
        if(a > b) return randomBetween(b, a);
        return rand() % (b-a+1) + a;
    }
};

/**
 * 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();
 */