Compute sum of all elements in 2 D array in C

In C programming, computing the sum of all elements in a 2D array involves traversing through each element using nested loops and accumulating the values. This is a fundamental operation when working with matrices and tabular data.

Syntax

datatype array_name[rows][columns];

For example: int arr[3][4]; creates a 2D array with 3 rows and 4 columns, containing 12 elements total.

Example 1: Sum of All Elements

Following is the C program to calculate the sum of all elements in a 2D array −

#include <stdio.h>

int main() {
    int arr[3][3] = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
    int sum = 0;
    int i, j;
    
    printf("2D Array elements:<br>");
    for(i = 0; i < 3; i++) {
        for(j = 0; j < 3; j++) {
            printf("%d ", arr[i][j]);
            sum += arr[i][j];
        }
        printf("<br>");
    }
    
    printf("Sum of all elements: %d<br>", sum);
    return 0;
}

2D Array elements:
1 2 3 
4 5 6 
7 8 9 
Sum of all elements: 45

Example 2: Sum of Even and Odd Elements

This example demonstrates how to calculate separate sums for even and odd elements in a 2D array −

#include <stdio.h>

int main() {
    int arr[2][3] = {{1, 2, 3}, {4, 5, 6}};
    int evenSum = 0, oddSum = 0;
    int i, j;
    
    printf("Array elements:<br>");
    for(i = 0; i < 2; i++) {
        for(j = 0; j < 3; j++) {
            printf("%d ", arr[i][j]);
            
            if(arr[i][j] % 2 == 0) {
                evenSum += arr[i][j];
            } else {
                oddSum += arr[i][j];
            }
        }
        printf("<br>");
    }
    
    printf("Sum of even elements: %d<br>", evenSum);
    printf("Sum of odd elements: %d<br>", oddSum);
    printf("Total sum: %d<br>", evenSum + oddSum);
    return 0;
}

Array elements:
1 2 3 
4 5 6 
Sum of even elements: 12
Sum of odd elements: 9
Total sum: 21

Key Points

• Use nested loops to traverse all elements: outer loop for rows, inner loop for columns
• Initialize sum variable to 0 before starting the calculation
• Array indexing starts from 0: arr[0][0] to arr[rows-1][columns-1]
• Time complexity: O(rows × columns), Space complexity: O(1)

Conclusion

Computing the sum of 2D array elements is straightforward using nested loops. This technique forms the foundation for more complex matrix operations and statistical calculations on tabular data.