/* Matrix Diagonal - Program to check whether a given matrix is diagonal matrix */

/*  A diagonal matrix is that square matrix whose diagonal elements from upper left to lower right are non-zero and all other elements are zero. For example,
2  0  0
0  4  0
0  0  6
*/

#include  <stdio.h>
#include  <conio.h>

void main()
{
    int  x[10][10], nr, nc, r, c, flag ;
    clrscr() ;
    printf("Enter the number of rows and columns: ") ;
    scanf("%d %d", &nr, &nc) ;
    if(nr==nc)  		/* checking for square matrix */
        {
            printf("Enter elements of the matrix: \n") ;
            for(r=0 ; r<nr ; r++)
                for(c=0 ; c<nc ; c++)
                    scanf("%d", &x[r][c]) ;
            flag=1 ;
            for(r=0 ; r<nr ; r++)
                for(c=0 ; c<nc ; c++)
                    if(r==c) /* true for diagonal elements */
                        {
                            if(x[r][c]==0)
                                flag=0;
                        }
                    else
                        {
                            if(x[r][c]!=0)
                                flag=0;
                        }
            if(flag==1)
                printf("The matrix is diagonal") ;
            else
                printf("The matrix is not diagonal") ;
        }
    else
        printf("The matrix is not a sqaure matrix") ;
    getch() ;
}

/*
Output1:

Enter the number of rows and columns: 3 3
Enter elements of the matrix:
11 0 0
0 22 0
0 0 44
The matrix is diagonal

Output2:

Enter the number of rows and columns: 3 3
Enter elements of the matrix:
11 0 2
0 22 0
0 0 44
The matrix is not diagonal

Output3:

Enter the number of rows and columns: 3  3
Enter elements of the matrix:
0 0 0
0 9 0
0 0 8
The matrix is not diagonal
*/