Sum of Each Row and Column in a Matrix using C

Introduction

In this tutorial, we will learn how to write a C program to find the sum of each row and each column in a matrix.

A matrix in C is a two-dimensional (2D) array that organizes data in rows and columns. It's like a table with rows going horizontally and columns going vertically. In C, a 2D array is declared as dataType arrayName[rows][columns].

This operation is used in many real-world applications, such as:

• Calculating total sales per product category (row sums)
• Finding total monthly revenue across different years (column sums)
• Image processing and data analysis
• Statistical calculations and spreadsheets

C Program to Find Row and Column Sums

#include <stdio.h>

#define MAX_ROWS 10
#define MAX_COLS 10

int main() {
    int matrix[MAX_ROWS][MAX_COLS];
    int rows, cols;
    int i, j;
    
    // Input dimensions
    printf("Enter number of rows (max %d): ", MAX_ROWS);
    scanf("%d", &rows);
    printf("Enter number of columns (max %d): ", MAX_COLS);
    scanf("%d", &cols);
    
    // Validate dimensions
    if(rows > MAX_ROWS || cols > MAX_COLS || rows <= 0 || cols <= 0) {
        printf("Invalid dimensions!\n");
        return 1;
    }
    
    // Input matrix elements
    printf("\nEnter matrix elements:\n");
    for(i = 0; i < rows; i++) {
        for(j = 0; j < cols; j++) {
            printf("Element [%d][%d]: ", i+1, j+1);
            scanf("%d", &matrix[i][j]);
        }
    }
    
    // Display the matrix
    printf("\nThe matrix is:\n");
    for(i = 0; i < rows; i++) {
        for(j = 0; j < cols; j++) {
            printf("%5d ", matrix[i][j]);
        }
        printf("\n");
    }
    
    // Calculate and display row sums
    printf("\n=== Row Sums ===\n");
    for(i = 0; i < rows; i++) {
        int rowSum = 0;
        for(j = 0; j < cols; j++) {
            rowSum += matrix[i][j];
        }
        printf("Row %d: %d\n", i+1, rowSum);
    }
    
    // Calculate and display column sums
    printf("\n=== Column Sums ===\n");
    for(j = 0; j < cols; j++) {
        int colSum = 0;
        for(i = 0; i < rows; i++) {
            colSum += matrix[i][j];
        }
        printf("Column %d: %d\n", j+1, colSum);
    }
    
    return 0;
}

Sample Output

Enter number of rows (max 10): 3
Enter number of columns (max 10): 3

Enter matrix elements:
Element [1][1]: 1
Element [1][2]: 2
Element [1][3]: 3
Element [2][1]: 4
Element [2][2]: 5
Element [2][3]: 6
Element [3][1]: 7
Element [3][2]: 8
Element [3][3]: 9

The matrix is:
    1     2     3 
    4     5     6 
    7     8     9 

=== Row Sums ===
Row 1: 6
Row 2: 15
Row 3: 24

=== Column Sums ===
Column 1: 12
Column 2: 15
Column 3: 18

Another Example:

Enter number of rows (max 10): 2
Enter number of columns (max 10): 4

Enter matrix elements:
Element [1][1]: 1
Element [1][2]: 2
Element [1][3]: 3
Element [1][4]: 4
Element [2][1]: 5
Element [2][2]: 6
Element [2][3]: 7
Element [2][4]: 8

The matrix is:
    1     2     3     4 
    5     6     7     8 

=== Row Sums ===
Row 1: 10
Row 2: 26

=== Column Sums ===
Column 1: 6
Column 2: 8
Column 3: 10
Column 4: 12

Program Explanation

Let's break down the code step by step:

1. Include Header File: #include <stdio.h> includes the standard input/output library.
2. Define Constants: #define MAX_ROWS 10 and #define MAX_COLS 10 set maximum matrix size.
3. Declare Variables:
   • int matrix[MAX_ROWS][MAX_COLS]; — the 2D array
   • int rows, cols; — dimensions of the matrix
   • int i, j; — loop counters
4. Input Matrix: Nested loops read values from the user into the matrix.
5. Display Matrix: Nested loops print the matrix in tabular format.
6. Calculate Row Sums: For each row, we initialize rowSum = 0 and add all elements in that row. The column index varies while the row index remains constant.
7. Calculate Column Sums: For each column, we initialize colSum = 0 and add all elements in that column. The row index varies while the column index remains constant.
8. Return: return 0; indicates successful program execution.

Step-by-Step Approach

Algorithm to Find Row and Column Sums

1. Start
2. Read the number of rows and columns
3. Read elements into the matrix using nested loops
4. For i = 0 to rows-1:
   • Set rowSum = 0
   • For j = 0 to cols-1:
     • rowSum += matrix[i][j]
   • Print rowSum
5. For j = 0 to cols-1:
   • Set colSum = 0
   • For i = 0 to rows-1:
     • colSum += matrix[i][j]
   • Print colSum
6. End

#include <stdio.h>

int main() {
    int matrix[10][10];
    int n, i, j;
    int diagSum = 0;
    
    printf("Enter the size of square matrix: ");
    scanf("%d", &n);
    
    printf("Enter matrix elements:\n");
    for(i = 0; i < n; i++) {
        for(j = 0; j < n; j++) {
            scanf("%d", &matrix[i][j]);
        }
    }
    
    // Calculate diagonal sum (main diagonal)
    for(i = 0; i < n; i++) {
        diagSum += matrix[i][i];
    }
    
    printf("Matrix:\n");
    for(i = 0; i < n; i++) {
        for(j = 0; j < n; j++) {
            printf("%5d ", matrix[i][j]);
        }
        printf("\n");
    }
    
    printf("Sum of diagonal elements: %d\n", diagSum);
    return 0;
}

#include <stdio.h>

int main() {
    int matrix[3][3];
    int i, j;
    
    printf("Enter 3x3 matrix elements:\n");
    for(i = 0; i < 3; i++) {
        for(j = 0; j < 3; j++) {
            scanf("%d", &matrix[i][j]);
        }
    }
    
    printf("\nMatrix:\n");
    for(i = 0; i < 3; i++) {
        for(j = 0; j < 3; j++) {
            printf("%5d ", matrix[i][j]);
        }
        printf("\n");
    }
    
    // Row sums
    printf("\nRow Sums:\n");
    for(i = 0; i < 3; i++) {
        int sum = 0;
        for(j = 0; j < 3; j++) {
            sum += matrix[i][j];
        }
        printf("Row %d: %d\n", i+1, sum);
    }
    
    // Column sums
    printf("\nColumn Sums:\n");
    for(j = 0; j < 3; j++) {
        int sum = 0;
        for(i = 0; i < 3; i++) {
            sum += matrix[i][j];
        }
        printf("Column %d: %d\n", j+1, sum);
    }
    
    return 0;
}

Frequently Asked Questions

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