find sum of diagonal element of a matrix in c

1#include <stdio.h>
2void main ()
3{
4    int i,j,matrix[10][10],m,n,sum=0;
5
6    printf("Enter number of rows of matrix  : ");
7    scanf("%d", &m);
8    printf("Enter number of columns of matrix  : ");
9    scanf("%d", &n);
10
11    printf("\n");
12
13    if(m==n)
14    {
15        for (i = 0; i < m; i++)
16        {
17            for (j = 0; j < n; j++)
18            {
19                printf("Enter element of matrix [%d][%d]: ", i, j);
20                scanf("%d", &matrix[i][j]);
21            }
22        }
23
24        printf("\n");
25
26        for(i=0;i<m;i++)
27        {
28            for(j=0;j<n;j++)
29            {
30                if(i==j)
31                {
32                    sum=sum+matrix[i][j];
33                }
34            }
35        }
36
37        printf("The sum of diagonal elements of the matrix = %d\n",sum);
38    }
39
40    else
41        printf("The matrix does not have diagonal elements");
42}
43
44
45

1#include<stdio.h>
2 
3void main()
4{
5    int mat[12][12];
6    int i,j,row,col,sum=0;
7    printf("Enter the number of rows and columns for 1st matrix\n");
8    scanf("%d%d",&row,&col);
9    printf("Enter the elements of the matrix\n");
10    for(i=0;i<row;i++)
11    {
12        for(j=0;j<col;j++)
13        {
14            scanf("%d",&mat[i][j]);
15        }
16    }
17 
18    printf("The matrix\n");
19    for(i=0;i<row;i++)
20    {
21        for(j=0;j<col;j++)
22        {
23            printf("%d\t",mat[i][j]);
24        }
25        printf("\n");
26    }
27    //To add diagonal elements
28    for(i=0;i<row;i++)
29    {
30        for(j=0;j<col;j++)
31        {
32            if(i==j)
33            {
34                sum=sum+mat[i][j];
35            }
36        }
37    }
38 
39    printf("The sum of diagonal elements of a square matrix = %d\n",sum);
40}
41