Example: Sum of Main Diagonal Elements in C

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// Sum of Main Diagonal Elements
#include <stdio.h>

int main() {
    // Step 1: Define the square matrix and its size
    int matrix[3][3] = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9}
    };
    int size = 3; // For a 3x3 matrix

    // Step 2: Initialize sum for the main diagonal
    int main_diagonal_sum = 0;

    // Step 3: Iterate through the matrix to find main diagonal elements
    // For a main diagonal element, the row index (i) is always equal to the column index (j)
    for (int i = 0; i < size; i++) {
        main_diagonal_sum += matrix[i][i]; // Add element at (i, i)
    }

    // Step 4: Print the result
    printf("Matrix:\n");
    for (int i = 0; i < size; i++) {
        for (int j = 0; j < size; j++) {
            printf("%d ", matrix[i][j]);
        }
        printf("\n");
    }
    printf("Sum of main diagonal elements: %d\n", main_diagonal_sum);

    return 0;
}