Find the sum of diagonals of a matrix

Find the sum of diagonals of a matrix


Input:

1      2     3     4     5
6      7     8     9    10
11   12   13   14   15
16   17   18   19   20
21   22   23   24   25

Output:

sum of leftdiagonal elements is:65
sum of rightdiagonal elements is:65

Implementation:

#include <stdio.h> #include <stdlib.h> /* change the row size & column size here */ #define r 5 #define c 5 /* function to find the left diagonal sum & right diagonal sum */ void finddiagonalsum(int *a[],int *left,int *right) { int i,j; for(i=0;i<r;i++) { for(j=0;j<c;j++) { /* add the left diagonal elements in the left */ if(i==j) *left += *(*(a+i)+j); /* add the right diagonal elements in the right */ if(j==(c-i-1)) *right += *(*(a+i)+j); } } } int main(void) { /* array of pointers to 'r' 1-D arrays */ int *a[r]; int i,j; /* initialize the left diagonal sum & right diagonal initially to be zero */ int left=0,right=0; /* allocate memory for 'r' 1-D arrays & return/store the address of those blocks in the array of poiners */ for(i=0;i<r;i++) *(a+i)=(int*)malloc(sizeof(int)*1000000); /* get the numbers / values of the matrix or 2-D array of rxc */ for(i=0;i<r;i++) { for(j=0;j<c;j++) { scanf("%d",(*(a+i)+j)); } } /* call the function passing array base address, address of left diagonal sum, address of right diagonal sum */ finddiagonalsum(a,&left,&right); /* print the left diagonal sum */ printf("sum of leftdiagonal elements is:%d",left); /* print the right diagonal sum */ printf("\nsum of rightdiagonal elements is:%d",right); return 0; }