Write a C program to read elements in a matrix and find the sum of minor diagonal (opposite diagonal) elements. C program to calculate sum of minor diagonal elements. Logic to find sum of opposite diagonal elements of a matrix in C programming.

**Example**

**Input**

Input elements in array: 1 2 3 4 5 6 7 8 9

**Output**

Sum of minor diagonal elements = 15

## Required knowledge

Basic C programming, For loop, Array

### Minor diagonal of a matrix

Minor diagonal of a matrix **A** is a collection of elements **A**_{ij} Such that *i + j = N + 1*.

Read more - Program to find sum of main diagonal element of a matrix

## Program to find sum of opposite diagonal elements of a matrix

```
/**
* C program to find sum of opposite diagonal elements of a matrix
*/
#include <stdio.h>
#define SIZE 3 // Matrix size
int main()
{
int A[SIZE][SIZE];
int row, col, sum = 0;
/* Input elements in matrix from user */
printf("Enter elements in matrix of size %dx%d: \n");
for(row=0; row<SIZE; row++)
{
for(col=0; col<SIZE; col++)
{
scanf("%d", &A[row][col]);
}
}
/* Find sum of minor diagonal elements */
for(row=0; row<SIZE; row++)
{
for(col=0; col<SIZE; col++)
{
/*
* If it is minor diagonal of matrix
* Minor diagonal: i+j == N + 1
* Since array elements starts from 0 hence i+j == (N + 1)-2
*/
if(row+col == ((SIZE+1)-2))
{
sum += A[row][col];
}
}
}
printf("\nSum of minor diagonal elements = %d", sum);
return 0;
}
```

Output

Enter elements in matrix of size 3x3: 1 2 3 4 5 6 7 8 9 Sum of minor elements = 15

Happy coding 😉

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