# Shuffle An Array Problem

## Description

LeetCode Problem 384.

Given an integer array nums, design an algorithm to randomly shuffle the array. All permutations of the array should be equally likely as a result of the shuffling.

Implement the Solution class:

• Solution(int[] nums) Initializes the object with the integer array nums.
• int[] reset() Resets the array to its original configuration and returns it.
• int[] shuffle() Returns a random shuffling of the array.

Example 1:

``````1
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Input
["Solution", "shuffle", "reset", "shuffle"]
[[[1, 2, 3]], [], [], []]
Output
[null, [3, 1, 2], [1, 2, 3], [1, 3, 2]]
Explanation
Solution solution = new Solution([1, 2, 3]);
solution.shuffle();    // Shuffle the array [1,2,3] and return its result.
// Any permutation of [1,2,3] must be equally likely to be returned.
// Example: return [3, 1, 2]
solution.reset();      // Resets the array back to its original configuration [1,2,3]. Return [1, 2, 3]
solution.shuffle();    // Returns the random shuffling of array [1,2,3]. Example: return [1, 3, 2]
``````

Constraints:

• 1 <= nums.length <= 200
• -10^6 <= nums[i] <= 10^6
• All the elements of nums are unique.
• At most 5 * 10^4 calls in total will be made to reset and shuffle.

## Sample C++ Code

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class Solution {
public:
vector<int> orig;
vector<int> tmp;

Solution(vector<int>& nums) {
orig = nums;
}

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

/** Returns a random shuffling of the array. */
vector<int> shuffle() {
int n = orig.size();
tmp = orig;
vector<int> ans;
while (n > 0) {
int r = rand() % n;
ans.push_back(tmp[r]);
tmp[r] = tmp[n-1];
n --;
}
return ans;
}
};

/**
* 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();
*/
``````