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# Javascript Program for Left Rotation and Right Rotation of a String

Given a string of size n, write functions to perform the following operations on a string-

1. Left (Or anticlockwise) rotate the given string by d elements (where d <= n)
2. Right (Or clockwise) rotate the given string by d elements (where d <= n).

Examples:

```Input : s = "GeeksforGeeks"
d = 2
Output : Left Rotation  : "eksforGeeksGe"
Right Rotation : "ksGeeksforGee"

Input : s = "qwertyu"
d = 2
Output : Left rotation : "ertyuqw"
Right rotation : "yuqwert"```

### Method 1:

A Simple Solution is to use a temporary string to do rotations. For left rotation, first, copy last n-d characters, then copy first d characters in order to the temporary string. For right rotation, first, copy last d characters, then copy n-d characters.

Can we do both rotations in-place and O(n) time?
The idea is based on a reversal algorithm for rotation.

```// Left rotate string s by d (Assuming d <= n)
leftRotate(s, d)
reverse(s, 0, d-1); // Reverse substring s[0..d-1]
reverse(s, d, n-1); // Reverse substring s[d..n-1]
reverse(s, 0, n-1); // Reverse whole string.

// Right rotate string s by d (Assuming d <= n)
rightRotate(s, d)

// We can also call above reverse steps
// with d = n-d.
leftRotate(s, n-d)  ```

Below is the implementation of the above steps :

## Javascript

 ``

Output:

```Left rotation:  eksforGeeksGe
Right rotation:  ksGeeksforGee                 ```

Time Complexity: O(N), as we are using a loop to traverse N times so it will cost us O(N) time
Auxiliary Space: O(1), as we are not using any extra space.

### Method 2:

We can use extended string which is double in size of normal string to rotate string. For left rotation, access the extended string from index n to the index len(string) + n. For right rotation, rotate the string left with size-d places.

#### Approach:

The approach is

```// Left rotate string s by d
leftRotate(s, n)
temp = s + s; // extended string
l1  = s.length // length of string
return temp[n : l1+n] //return rotated string.

// Right rotate string s by n
rightRotate(s, n)
// We can also call above reverse steps
// with x = s.length - n.
leftRotate(s, x-n)```

Below is implementation of above approach:

## Javascript

 `// JavaScript program for Left Rotation and Right``// Rotation of a String` `// Function that rotates string towards left by n``function` `leftrotate(str1, n)``{``    ``var` `temp = str1 + str1;``    ``var` `l1 = str1.length;``    ` `    ``var` `Lfirst = temp.substr(n,l1);` `//     now returning string``    ``return` `Lfirst;``}` `// Function that rotates string towards right by n``function` `rightrotate(str, d)``{``    ``return` `leftrotate(str, str.length - d);``}` `// Driver code``var` `str1 = ``"GeeksforGeeks"``;``console.log(leftrotate(str1, 2));` `var` `str2 = ``"GeeksforGeeks"``;``console.log(rightrotate(str2, 2) );` `// This code is contributed by Susobhan Akhuli`

Output

```eksforGeeksGe
ksGeeksforGee```

Time Complexity: O(N), where N is the size of the given string.
Auxiliary Space: O(N)

Please refer complete article on Left Rotation and Right Rotation of a String for more details!

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