/* Matrix Sum - Program to find sum of diagonal elements, elements above diagonal and elements below diagonal of a given square matrix */

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

void  main()
{
    int  x[10][10], nr, nc, r, c, sumd=0, suma=0, sumb=0 ;
    clrscr() ;
    printf("Enter the number of rows and columns: ") ;
    scanf("%d %d", &nr, &nc) ;
    printf("Enter elements of the matrix row-wise: \n") ;
    for(r=0 ; r<nr ; r++)
        for(c=0 ; c<nc ; c++)
            scanf("%d", &x[r][c]) ;
    for(r=0 ; r<nr ; r++)
        for(c=0 ; c<nc ; c++)
            {
                if(r==c)
                    sumd = sumd + x[r][c] ;
                if(r<c)
                    suma = suma + x[r][c] ;
                if(r>c)
                    sumb = sumb + x[r][c] ;
            }
    printf("The sum of all diagonal elements is %d \n", sumd) ;
    printf("The sum of elements above diagonal is %d \n", suma) ;
    printf("The sum of elements below diagonal is %d \n", sumb) ;
    getch() ;
}

/* The following logic is also correct
  for(r=0 ; r<nr ; r++)
    for(c=0 ; c<nc ; c++)
    {
      if(r==c)
        sumd = sumd + x[r][c] ;
      if(r<c)
      {
        suma = suma + x[r][c] ;
        sumb = sumb + x[c][r] ;  <---- SEE HERE CAREFULLY
      }
    }
*/


/*
Output:

Enter the number of rows and columns: 3 3
Enter elements of the matrix row-wise:
1 2 3
4 5 6
7 8 9
The sum of all diagonal elements is 15
The sum of elements above diagonal is 11
The sum of elements below diagonal is 19
*/