# 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**

*


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://code-snippets.hbamithkumara.com/leetcode/problems/301-400/shuffle-an-array.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.