Print a matrix in reverse spiral form

Posted on Apr 26, 2020

C program to print a matrix in reverse spiral form.

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 print_antispiral(int mat[MAX][MAX], int row, int col)
{
    int left, right, top, bottom, i;
    int arr[MAX*MAX], count;

    left = 0;
    right = col-1;
    top = 0;
    bottom = row-1;

    count = 0;
    while(left <= right && top <= bottom)
    {
        for(i=left;i<=right;i++)
        {
            arr[count] = mat[top][i];
            count++;
        }
        top++;

        for(i=top;i<=bottom;i++)
        {
            arr[count] = mat[i][right];
            count++;
        }
        right--;

        if(top <= bottom)
        {
            for(i=right;i>=left;i--)
            {
                arr[count] = mat[bottom][i];
                count++;
            }
            bottom--;
        }

        if(left <= right)
        {
            for(i=bottom;i>=top;i--)
            {
                arr[count] = mat[i][left];
                count++;
            }
            left++;
        }
    }

    for(i=count-1;i>=0;i--)
    {
        printf("%d  ",arr[i]);
    }
}

void main()
{
    int 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);

    printf("\nMatrix in antispiral form is \n");
    print_antispiral(mat, row, col);

    getch();
}

Output

Enter the number of rows        :6
Enter the number of columns     :4
Enter the elements of the matrix
Element [0][0]  :1
Element [0][1]  :2
Element [0][2]  :3
Element [0][3]  :4
Element [1][0]  :5
Element [1][1]  :6
Element [1][2]  :7
Element [1][3]  :8
Element [2][0]  :9
Element [2][1]  :10
Element [2][2]  :11
Element [2][3]  :12
Element [3][0]  :13
Element [3][1]  :14
Element [3][2]  :15
Element [3][3]  :16
Element [4][0]  :17
Element [4][1]  :18
Element [4][2]  :19
Element [4][3]  :20
Element [5][0]  :21
Element [5][1]  :22
Element [5][2]  :23
Element [5][3]  :24

Matrix entered is
1       2       3       4
5       6       7       8
9       10      11      12
13      14      15      16
17      18      19      20
21      22      23      24

Matrix in antispiral form is
10  14  18  19  15  11  7  6  5  9  13  17  21  22  23  24  20  16  12  8  4  3  2  1