# Shuffle an Array - (Leetcode 384) - Coding Interview Question Mani
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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:

```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`
• `-106 <= nums[i] <= 106`
• All the elements of `nums` are unique.
• At most `5 * 104` calls in total will be made to `reset` and `shuffle`.

Solution:

``````1
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/**
* Optimized solution is :  Fisher-Yates Algorithm
* This involves following steps
* 1. Start with first index say start.
* 2. Pick a random index from range [start, arr.length)
* 3. Swap start index element with element at random index.
* 4. Increment start and continue above steps till end is reached.
* Time Complexity: O(N)
* Space Complexity: O(N).
*/
class Solution {

int[] a;

public Solution(int[] nums) {
a = nums;
}

/**
* Resets the array to its original configuration and return it.
*/
public int[] reset() {
return a;
}

/**
* Returns a random shuffling of the array.
*/
public int[] shuffle() {
int[] res = a.clone();
for (int i = 0; i < res.length; i++) {
int rand = i + (int) (Math.random() * (res.length - i));
int temp = res[i];
res[i] = res[rand];
res[rand] = temp;
}
return res;
}
}

/**
* Your Solution object will be instantiated and called as such:
* Solution obj = new Solution(nums);
* int[] param_1 = obj.reset();
* int[] param_2 = obj.shuffle();
*/
``````
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