C Programming Code Examples

C > Arrays and Matrices Code Examples

C program to right rotate an array



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.

    Read elements in an array say arr.
    Read number of times to rotate in some variable say N.
    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

Begin:
    read(arr)
    read(n)
    For j=1 to n do
        rotateArrayByOne(arr)
    End for
End
rotateArrayByOne(arr[], SIZE)
Begin:
    last = arr[SIZE - 1]
    For j = SIZE-1 to 0 do
        arr[j] = arr[j - 1]
    End for
    arr[0] = last
End

/* 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 j, N;
    int arr[SIZE];

    printf("Enter 10 elements array: ");
    for(j=0; j<SIZE; j++)
    {
        scanf("%d", &arr[j]);
    }
    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(j=1; j<=N; j++)
    {
        rotateByOne(arr);
    }

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

    return 0;
}

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

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

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

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

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

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