C program to right rotate an array

Write a C program to right rotate an array by n position. How to right rotate an array n times in C programming. Logic to rotate an array to right by n position in C program.

Right array rotation

Example

Input

Input 10 elements in array: 1 2 3 4 5 6 7 8 9 10
Input number of times to rotate: 3

Output

Array after right rotation: 8 9 10 1 2 3 4 5 6 7

Required knowledge

Basic C programming, Loop, Array, Function

Logic to right rotate an array

Below is the step by step descriptive logic to rotate an array to right by N positions.

  1. Read elements in an array say arr.
  2. Read number of times to rotate in some variable say N.
  3. Right rotate the given array by 1 for N times. In real right rotation is shifting of array elements to one position right and copying last element to first.

Algorithm to right rotate an array

Algorithm to right rotate an array
Begin:
    read(arr)
    read(n)
    For i←1 to n do
        rotateArrayByOne(arr)
    End for
End
rotateArrayByOne(arr[], SIZE)
Begin:
    lastarr[SIZE - 1]
    For iSIZE-1 to 0 do
        arr[i] ← arr[i - 1]
    End for
    arr[0] ← last
End

Program to right rotate an array

/**
 * C program to right rotate an array
 */

#include <stdio.h>
#define SIZE 10 /* Size of the array */

void printArray(int arr[]);
void rotateByOne(int arr[]);


int main()
{
    int i, N;
    int arr[SIZE];

    printf("Enter 10 elements array: ");
    for(i=0; i<SIZE; i++)
    {
        scanf("%d", &arr[i]);
    }
    printf("Enter number of times to right rotate: ");
    scanf("%d", &N);

    /* Actual rotation */
    N = N % SIZE;

    /* Print array before rotation */
    printf("Array before rotationn");
    printArray(arr);

    /* Rotate array n times */
    for(i=1; i<=N; i++)
    {
        rotateByOne(arr);
    }

    /* Print array after rotation */
    printf("\n\nArray after rotation\n");
    printArray(arr);

    return 0;
}


void rotateByOne(int arr[])
{
    int i, last;

    /* Store last element of array */
    last = arr[SIZE - 1];

    for(i=SIZE-1; i>0; i--)
    {
        /* Move each array element to its right */
        arr[i] = arr[i - 1];
    }

    /* Copy last element of array to first */
    arr[0] = last;
}


/**
 * Print the given array
 */
void printArray(int arr[])
{
    int i;

    for(i=0; i<SIZE; i++)
    {
        printf("%d ", arr[i]);
    }
}

Read more - Program to left rotate an array

Output

Enter 10 elements array: 1 2 3 4 5 6 7 8 9 10
Enter number of times to right rotate: 3
Array before rotation
1 2 3 4 5 6 7 8 9 10

Array after rotation
8 9 10 1 2 3 4 5 6 7

Happy coding 😉

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