Thread: Adding-up Elements of a Two-Dimensional Array

How would you do it on paper?

Originally Posted by setleaf

Well, this:

Code:

sum = arr[0][0] + arr [0][5];
cout << sum <<" ";

would give you your first sum of 7, and:

wrong. it should be:

Code:

sum = arr[0][0] + arr [1][0];
cout << sum <<" ";

Originally Posted by setleaf

Code:

sum = arr[0][1] + arr[1][1];
cout << sum <<" ";

would give you your second sum of 9.

This one is correct.

In addition, you should really be defining constants for the size of your array and loop iterations.

Code:

#include <iostream>
#include <conio.h>
using namespace std;

const int rows = 2;
const int columns = 5;

int main ()
{
    int arr [rows] [columns];
    int val = 1;
 
 
     
    for (int i = 0; i < rows; i++)
    {
        for (int j = 0; j < columns; j++)
        {
            //etc...

It might also be a good idea to change i and j to row and column, respectively. Descriptive variable names are to be preferred over single-letters.

Good to hear that it works for you, but you need to work on your code formatting, particularly your indentation. For example:

Code:

#include <iostream>
#include <conio.h>

using namespace std;

int main()
{
    int arr[2][5];
    int val = 1;

    for (int i = 0; i < 2; i++)
    {
        for (int j = 0; j < 5; j++)
        {
            arr[i][j] = val;
            val++;
        }
    }

    int sum[5] = {0};
    for (int j = 0; j < 5; j++)
    {
        for (int i = 0; i < 2; i++)
        {
            sum[j] += arr[i][j];
        }
    }

    for (int j = 0; j < 5; j++)
    {
        cout << sum[j] << " ";
    }
    cout << endl;

    getch();
    return 0;
}

Keep in mind that <conio.h> and getch are non-standard, and that you do not actually need them here since you can either run your program from a separate command prompt window, configure your IDE to pause your program before it exits, or use standard facilities to pause your program before it exits.

Also, instead of using the magic numbers 2 and 5 all over the place, you should have defined named constants.