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# 384. Shuffle an Array

### Description

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.

### 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`.

### Approach

### Links

* Binarysearch
* GeeksforGeeks
* [Leetcode](https://leetcode.com/problems/shuffle-an-array/)
* [ProgramCreek](https://www.programcreek.com/2014/08/leetcode-shuffle-an-array-java/)
* YouTube

### **Examples**

{% tabs %}
{% tab title="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]
{% endtab %}
{% endtabs %}

### **Solutions**

{% tabs %}
{% tab title="Solution 1" %}

```java
/**
 * Time complexity : 
 * Space complexity : 
 */

class Solution {
    private static final Random random = new Random();
    private final int arrLen;
    private int[] original, shuffled;

    public Solution(int[] nums) {
        arrLen = nums.length;
        original = nums;
        shuffled = Arrays.copyOf(original, arrLen);
    }
    
    /** Resets the array to its original configuration and return it. */
    public int[] reset() {
        shuffled = Arrays.copyOf(original, arrLen);
        return shuffled;
    }
    
    /** Returns a random shuffling of the array. */
    public int[] shuffle() {
        for(int i = 0; i < arrLen; i++) {
            int index = random.nextInt(arrLen-i) + i;
            int temp = shuffled[index];
            shuffled[index] = shuffled[i];
            shuffled[i] = temp;
        }
        return shuffled;
    }
}

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

{% endtab %}
{% endtabs %}

### **Follow up**

*