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Ruby program to calculate the sum of left diagonal the matrix

Last Updated : December 15, 2025

Problem Solution

In this program, we will create a matrix using the 2D array. Then we read elements of the matrix from the user. After that, we will calculate the sum of the left diagonal matrix and print the result.

Program/Source Code

The source code to calculate the sum of left diagonal the matrix is given below. The given program is compiled and executed successfully.

# Ruby program to calculate the sum of 
# left diagonal the matrix

TwoDArr = Array.new(3){Array.new(3)}
sum = 0;

printf "Enter elements of MATRIX:\n";
i = 0;
while (i < 3) 
  j = 0;
  while (j < 3) 
    printf "ELEMENT [%d][%d]: ", i, j;
    TwoDArr[i][j] =  gets.chomp.to_i;
    j = j + 1;
  end
  i = i + 1;
end

printf "MATRIX:\n";
i = 0;
while (i < 3)
  j = 0;
  while (j < 3) 
    print TwoDArr[i][j]," ";
    j = j + 1;
  end
  i = i + 1;
  print "\n";
end

printf("Left diagonal of matrix:\n")
i = 0;
while (i < 3) 
    j = 0;
    while (j < 3) 
        if (i == j)
            sum = sum + TwoDArr[i][j];
            printf "%d ", TwoDArr[i][j];
        else
            printf(" ");
        end
        j = j + 1;
    end
    i = i + 1;
    print "\n";
end

printf "Sum of left diagonal of matrix: %d\n",sum;

Output

Enter elements of MATRIX:
ELEMENT [0][0]: 1
ELEMENT [0][1]: 2
ELEMENT [0][2]: 3
ELEMENT [1][0]: 4
ELEMENT [1][1]: 5
ELEMENT [1][2]: 6
ELEMENT [2][0]: 7
ELEMENT [2][1]: 8
ELEMENT [2][2]: 9
MATRIX:
1 2 3 
4 5 6 
7 8 9 
Left diagonal of matrix:
1   
 5  
  9 
Sum of left diagonal of matrix: 15

Explanation

In the above program, we created a 3X3 matrix TwoDArr using the 2D array. Then we read the elements of the matrix. After that, we calculated the sum of left diagonal elements and printed the result.

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