Shuffle an Array

LeetCode #384

Description:

Shuffle a set of numbers without duplicates.

Example:

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();

Idea:

int rand (void); Generate random number Returns a pseudo-random integral number in the range between 0 and RAND_MAX.

Code:

class Solution {
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() {
        if(nums.empty()) return nums;
        vector<int> result(nums);
        int remainLen;
        for(int i=0; i<result.size()-1; ++i){
            remainLen=result.size()-i;
            int j = rand()%remainLen + i; // generate random number [i, N-1]
            swap(result[i], result[j]);
        }
        return result;
    }

private:
    vector<int> nums;
};

/**
 * 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();
 */