Rotate a matrix by 90 degree in clockwise direction

Posted on Apr 26, 2020

C program to rotate a matrix by 90 degree in clockwise direction.

Program

#include<stdio.h>
#include<conio.h>
#define MAX 10

void read_matrix(int mat[MAX][MAX], int row, int col)
{
    int i, j;
    for(i=0;i<row;i++)
    {
        for(j=0;j<col;j++)
        {
            printf("Element [%d][%d]\t:",i,j);
            scanf("%d",&mat[i][j]);
        }
    }
}

void print_matrix(int mat[MAX][MAX], int row, int col)
{
    int i, j;
    for(i=0;i<row;i++)
    {
        for(j=0;j<col;j++)
        {
            printf("%d\t",mat[i][j]);
        }
        printf("\n");
    }
}

void transpose(int mat[MAX][MAX], int rotate_mat[MAX][MAX], int row, int col)
{
    int i, j;

    for(i=0;i<row;i++)
    {
        for(j=0;j<col;j++)
        {
            rotate_mat[j][i] = mat[i][j];
        }
    }
}

void rev_row(int rotate_mat[MAX][MAX], int col, int row)
{
    int i, j, k, temp;

    for(i=0;i<col;i++)
    {
        for(j=0,k=row-1;j<k;j++,k--)
        {
            temp = rotate_mat[i][j];
            rotate_mat[i][j] = rotate_mat[i][k];
            rotate_mat[i][k] = temp;
        }
    }
}

void rotate90clock(int mat[MAX][MAX], int rotate_mat[MAX][MAX], int row, int col)
{
    transpose(mat, rotate_mat, row, col);
    rev_row(rotate_mat, col, row);
}

void main()
{
    int mat[MAX][MAX], rotate_mat[MAX][MAX];
    int row, col;

    printf("Enter the number of rows\t:");
    scanf("%d",&row);
    printf("Enter the number of columns\t:");
    scanf("%d",&col);

    printf("Enter the elements of the matrix\n");
    read_matrix(mat, row, col);

    printf("\nMatrix entered is\n");
    print_matrix(mat, row, col);

    rotate90clock(mat, rotate_mat, row, col);

    printf("\nMatrix after rotating clockwise 90 degree is\n");
    print_matrix(rotate_mat, col, row);

    getch();
}

Output

Enter the number of rows        :4
Enter the number of columns     :3
Enter the elements of the matrix
Element [0][0]  :1
Element [0][1]  :2
Element [0][2]  :3
Element [1][0]  :4
Element [1][1]  :5
Element [1][2]  :6
Element [2][0]  :7
Element [2][1]  :8
Element [2][2]  :9
Element [3][0]  :10
Element [3][1]  :11
Element [3][2]  :12

Matrix entered is
1       2       3
4       5       6
7       8       9
10      11      12

Matrix after rotating clockwise 90 degree is
10      7       4       1
11      8       5       2
12      9       6       3