Javascript Program to Print all possible rotations of a given Array

Given an integer array arr[] of size N, the task is to print all possible rotations of the array.
Examples: 

Input: arr[] = {1, 2, 3, 4} 
Output: {1, 2, 3, 4}, {4, 1, 2, 3}, {3, 4, 1, 2}, {2, 3, 4, 1} 
Explanation: 
Initial arr[] = {1, 2, 3, 4} 
After first rotation arr[] = {4, 1, 2, 3} 
After second rotation arr[] = {3, 4, 1, 2} 
After third rotation arr[] = {2, 3, 4, 1} 
After fourth rotation, arr[] returns to its original form.
Input: arr[] = [1] 
Output: [1] 

Approach 1: 
Follow the steps below to solve the problem:  

1. Generate all possible rotations of the array, by performing a left rotation of the array one by one.
2. Print all possible rotations of the array until the same rotation of array is encountered.

Below is the implementation of the above approach : 

<script>

// javascript program to print
// all possible rotations
// of the given array

// Global declaration of array
arr = Array.from({length: 10000}, (_, i) => 0);

// Function to reverse array 
// between indices s and e
function reverse(arr, s , e)
{
    while(s < e)
    {
        var tem = arr[s];
        arr[s] = arr[e];
        arr[e] = tem;
        s = s + 1;
        e = e - 1;
    }
}

// Function to generate all
// possible rotations of array
function fun(arr , k)
{
    var n = 4 - 1;
    var v = n - k;
    
    if (v >= 0)
    {
        reverse(arr, 0, v);
        reverse(arr, v + 1, n);
        reverse(arr, 0, n);
    }
}

// Driver code

    arr[0] = 1;
    arr[1] = 2;
    arr[2] = 3;
    arr[3] = 4;
    
    for(i = 0; i < 4; i++)
    {
        fun(arr, i);
        
        document.write("[");
        for(j = 0; j < 4; j++)
        {
            document.write(arr[j] + ", ");
        }
        document.write("]<br>");
    }


// This code is contributed by 29AjayKumar 
</script>

[1, 2, 3, 4] [4, 1, 2, 3] [2, 3, 4, 1] [3, 4, 1, 2]

Time Complexity: O (N²) 
Auxiliary Space: O (1)

Approach 2: Follow the steps below to solve the problem:  

1. Initialize an array arr and get its length.
2. Create a new array rotatedArr of twice the length of arr.
3. Copy the elements of arr into rotatedArr twice, once in the first half and then in the second half starting from the index equal to the length of arr.
4. Iterate over the indices from 0 to the length of arr and generate all possible rotations by printing the sub-array starting from that index and having the length equal to the length of arr. The sub-array is formed by iterating over the elements of rotatedArr starting from the index i and ending at index i+n-1, where n is the length of arr.

Below is the implementation of the above approach: 

let arr = [1, 2, 3, 4];
let n = arr.length;

let rotatedArr = new Array(2*n);

// Copy the array twice into the rotatedArr
for (let i = 0; i < n; i++) {
    rotatedArr[i] = arr[i];
    rotatedArr[i+n] = arr[i];
}
// Nikunj Sonigara
// Generate all possible rotations
for (let i = 0; i < n; i++) {
    let str = "[";
    for (let j = i; j < i+n; j++) {
        str += rotatedArr[j];
        if(j != i+n-1)
            str += " ";
    }
    str += "] ";
    console.log(str);
}

[1 2 3 4] 
[2 3 4 1] 
[3 4 1 2] 
[4 1 2 3] 

Time Complexity: O(N²) 
Auxiliary Space: O(N)

Please refer complete article on Print all possible rotations of a given Array for more details!