C++ Program to Find Sum of Opposite Diagonal of a Matrix

Write a C++ Program to Find the Sum of Opposite Diagonal of a Matrix with an example. Within the C++ for loop, we are adding the value of all the opposite diagonal values of the given matrix.

#include<iostream>
using namespace std;

int main()
{
	int i, j, rows, columns, sum = 0;
	
	cout << "\nPlease Enter the Matrix rows and Columns =  ";
	cin >> i >> j;
	
	int sumOppDgnalArr[i][j];
	
	cout << "\nPlease Enter the Matrix Items\n";
	for(rows = 0; rows < i; rows++)	{
		for(columns = 0; columns < i; columns++) {
			cin >> sumOppDgnalArr[rows][columns];
		}		
	}

 	for(rows = 0; rows < i; rows++)
  	{
  		sum = sum + sumOppDgnalArr[rows][i - rows  - 1];
  	}
  	
  	cout << "\nThe Sum of Opposite Diagonal Elements of a Matrix = " << sum;

 	return 0;
}

i = 3, rows = 0
sum = sum + sumOppDgnalArr[0][3 – 0 – 1] => sum + sumOppDgnalArr[0][2]
sum = 0 + 30

i = 3, rows = 1, and sum = 30
sum = sum + sumOppDgnalArr[1][1]
sum = 30 + 90 = 120

i = 3, rows = 2, and sum = 120

sum = sum + sumOppDgnalArr[2][0]

sum = 120 + 70 = 190

C++ Program to Find Sum of Opposite Diagonal of a Matrix Example 2

In this C++ example, we added two extra cout statements to show you the iteration number, row value, and sum at each iteration.

#include<iostream>
using namespace std;

int main()
{
	int i, j, rows, columns, sum = 0;
	
	cout << "\nPlease Enter the Matrix rows and Columns =  ";
	cin >> i >> j;
	
	int sumOppDgnalArr[i][j];
	
	cout << "\nPlease Enter the Matrix Items\n";
	for(rows = 0; rows < i; rows++)	{
		for(columns = 0; columns < i; columns++) {
			cin >> sumOppDgnalArr[rows][columns];
		}		
	}

 	for(rows = 0; rows < i; rows++)
  	{
  		cout << "\nIteration = " << rows + 1 << ", Row Number = " << rows << " and Sum = " << sum;
  		sum = sum + sumOppDgnalArr[rows][i - rows  - 1]; 		
		cout <<  "\nsumOppDgnalArr["<<rows<<"]["<< i - rows - 1 <<"] = " << sumOppDgnalArr[rows][i - rows - 1] << 
			" and sum + sumOppDgnalArr["<<rows<<"]["<< i - rows - 1 <<"] = " << sum << endl;
  	}
  	
  	cout << "\nThe Sum of Opposite Diagonal Elements of a Matrix = " << sum;

 	return 0;
}

Please Enter the Matrix rows and Columns =  2 2

Please Enter the Matrix Items
11 22
99 122

Iteration = 1, Row Number = 0 and Sum = 0
sumOppDgnalArr[0][1] = 22 and sum + sumOppDgnalArr[0][1] = 22

Iteration = 2, Row Number = 1 and Sum = 22
sumOppDgnalArr[1][0] = 99 and sum + sumOppDgnalArr[1][0] = 121

The Sum of Opposite Diagonal Elements of a Matrix = 121

It is another approach to write a C++ Program to calculate the Sum of Matrix Opposite Diagonal.

#include<iostream>
using namespace std;

int main()
{
	int i, j, rows, columns, sum = 0;
	
	cout << "\nPlease Enter the Matrix rows and Columns =  ";
	cin >> i >> j;
	
	int sumOppDgnalArr[i][j];
	
	cout << "\nPlease Enter the Matrix Items\n";
	for(rows = 0; rows < i; rows++)	{
		for(columns = 0; columns < i; columns++) {
			cin >> sumOppDgnalArr[rows][columns];
		}		
	}

 	for(rows = 0; rows < i; rows++)
  	{
  		for(columns = 0;columns < j; columns++)
  		{
  			if(rows + columns == ((i + 1) - 2))
			{
  				sum = sum + sumOppDgnalArr[rows][columns];
			}		
		}		
  	}
  	
  	cout << "\nThe Sum of Opposite Diagonal Elements of a Matrix = " << sum;

 	return 0;
}

Please Enter the Matrix rows and Columns =  3 3

Please Enter the Matrix Items
11 22 33
44 55 65
99 10 122

The Sum of Opposite Diagonal Elements of a Matrix = 187