C program for array rotation has been shown here. An array rotation is described as the rotation of array elements to either left or right by k positions.

Example 1: Left rotation

Given array A[] = {10, 20, 30, 40, 50, 60}, k = 2

Rotate elements of A[] by 1 position to the left.

=>A[] = {20, 30, 40, 50, 60, 10}

Again rotate elements of A[] by 1 position to the left.

=>A[] = {30, 40, 50, 60, 10, 20}

So, array A[] after left rotation by 2 positions: {30, 40, 50, 60, 10, 20}

Example 2: Right rotation

Given array A[] = {10, 20, 30, 40, 50, 60}, k = 2

Rotate elements of A[] by 1 position to the right.

=>A[] = {60, 10, 20, 30, 40, 50}

Again rotate elements of A[] by 1 position to the left.

=>A[] = {50, 60, 10, 20, 30, 40}

So, array A[] after right rotation by 2 positions: {50, 60, 10, 20, 30, 40}

## 1. C program & output to Rotate an Array

Code has been copied
/*****************************
alphabetacoder.com
C program to rotate an array
******************************/

#include<stdio.h>

int main() {
// declare variables
int i, j, k, s, d, e;
int arr[20] = {0};

// take input
printf("Enter the size of array: ");
scanf("%d", & s);

// take input
printf("Enter the elements of array: ");
for (i = 0; i < s; i++) {
scanf("%d", & arr[i]);
}

// take input of the direction of rotation
printf("Enter the direction of rotation: \n");
printf("1. Left rotation\n");
printf("2. Right rotation\n");
scanf("%d", & d);

switch (d) {
case 1:
// take input of the number of position of rotation
printf("Enter the number of position to be left shifted: ");
scanf("%d", & k);

// left shift the array upto k position
for (i = 0; i < k; i++) {
// get the first elements
e = arr[0];
for (j = 0; j < s - 1; j++) {
arr[j] = arr[j + 1];
}
arr[s - 1] = e;
}
// display the array
printf("Output array: ");
for (i = 0; i < s; i++) {
printf("%d ", arr[i]);
}
break;
case 2:
// take input of the number of position of rotation
printf("Enter the number of position to be right shifted: ");
scanf("%d", & k);

// right shift the array upto k position
for (i = 0; i < k; i++) {
// get the first elements
e = arr[s - 1];
for (j = s - 1; j > 0; j--) {
arr[j] = arr[j - 1];
}
arr[0] = e;
}
// display the array
printf("Output array: ");
for (i = 0; i < s; i++) {
printf("%d ", arr[i]);
}
break;
default:
printf("Wrong choice!");
break;
}
}


Output

#### Case 1:

Enter the size of array: 5

Enter the elements of array: 0 5 10 15 20

Enter the direction of rotation:

1. Left rotation

2. Right rotation

Enter the number of position to be left shifted: 3

Output array:

15 20 0 5 10

#### Case 2:

Enter the size of array: 5

Enter the elements of array: 0 5 10 15 20

Enter the direction of rotation:

1. Left rotation

2. Right rotation

Enter the number of position to be right shifted: 3

Output array:

10 15 20 0 5

## 2. Time complexity to Rotate an Array

Time Complexity: O(n * k)

Here, $n$ elements in an array are to be rotated by $k$ positions to either left or right.