384. Shuffle an Array

https://leetcode.com/problems/shuffle-an-array/description/
class Solution {
    vector<int> nums;
public:
    Solution(vector<int> nums) {
        this->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() {
        int N = nums.size();
        vector<int> res(nums);
        for(int i=0; i<N; i++) {
            int j = rand() % (N-i);
            swap(res[i], res[i+j]);
        }
        return res;
    }
};