Find the Sum of All Elements in a 2D Array in C

To find the sum of all elements in a 2D array in C, we need to iterate through each row and column, adding up all the values. This is commonly done using nested loops, where the outer loop traverses the rows and the inner loop traverses the columns, accumulating the sum in a variable.

Examples to Find Sum of Elements in a 2D Array

1. Finding Sum of All Elements Using Nested Loops

In this example, we will define a 2D array and use nested loops to traverse each element, summing them up into a variable.

main.c

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#include <stdio.h>

int main() {
    int arr[3][3] = {
        {1, 2, 3},
        {4, 5, 6},
        {7, 8, 9}
    };
    
    int sum = 0;

    // Iterating through each element using nested loops
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 3; j++) {
            sum += arr[i][j]; // Adding each element to sum
        }
    }

    printf("Sum of all elements: %d\n", sum);

    return 0;
}

Explanation:

  1. We declare a 3x3 integer array arr and initialize it with values.
  2. We initialize an integer variable sum to store the total sum, starting at 0.
  3. We use a nested loop where the outer loop (i) iterates over the rows and the inner loop (j) iterates over the columns.
  4. Inside the inner loop, we add each element arr[i][j] to the sum variable.
  5. After both loops finish, we print the final sum.

Output:

Sum of all elements: 45

2. Finding Sum Using a Function

In this example, we will define a function to calculate the sum of a 2D array and call it from the main function.

main.c

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#include <stdio.h>

#define ROWS 2
#define COLS 3

// Function to calculate sum of a 2D array
int sumOfArray(int arr[ROWS][COLS]) {
    int sum = 0;
    for (int i = 0; i < ROWS; i++) {
        for (int j = 0; j < COLS; j++) {
            sum += arr[i][j];
        }
    }
    return sum;
}

int main() {
    int numbers[ROWS][COLS] = {
        {1, 2, 3},
        {4, 5, 6}
    };

    int total = sumOfArray(numbers);
    printf("Sum of all elements: %d\n", total);

    return 0;
}

Explanation:

  1. We define constants ROWS and COLS to specify the array dimensions.
  2. We declare a function sumOfArray() that takes a 2D array as input.
  3. Inside the function, we use nested loops to iterate through the array and sum the elements.
  4. In main(), we declare a 2x3 array numbers and initialize it with values.
  5. We call sumOfArray() and store the returned sum in total.
  6. We print the total sum.

Output:

Sum of all elements: 21

3. Finding Sum of Elements in a Dynamically Sized 2D Array

In this example, we will take user input for the number of rows and columns, dynamically allocate memory for the 2D array, and compute the sum.

main.c

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#include <stdio.h>
#include <stdlib.h>

int main() {
    int rows, cols;

    // Taking user input for dimensions
    printf("Enter number of rows: ");
    scanf("%d", &rows);
    printf("Enter number of columns: ");
    scanf("%d", &cols);

    // Dynamically allocating memory for 2D array
    int **arr = (int **)malloc(rows * sizeof(int *));
    for (int i = 0; i < rows; i++) {
        arr[i] = (int *)malloc(cols * sizeof(int));
    }

    // Taking user input for array elements
    printf("Enter elements of the array:\n");
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            scanf("%d", &arr[i][j]);
        }
    }

    int sum = 0;

    // Calculating sum
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            sum += arr[i][j];
        }
    }

    printf("Sum of all elements: %d\n", sum);

    // Free allocated memory
    for (int i = 0; i < rows; i++) {
        free(arr[i]);
    }
    free(arr);

    return 0;
}

Explanation:

  1. We take user input for rows and columns.
  2. We dynamically allocate memory using malloc().
  3. We take user input for array elements.
  4. We use nested loops to calculate the sum.
  5. Finally, we free the allocated memory.

Output:

Enter number of rows: 2
Enter number of columns: 3
Enter elements of the array:
1 2 3 4 5 6
Sum of all elements: 21

Conclusion

In this tutorial, we covered different methods to find the sum of all elements in a 2D array, including nested loops, functions, and dynamic memory allocation.