二维数组及其元素的总和

Question

In this program I'm trying to add the elements of a 2d array, print the entire array, and print its sum using functions. I know I am very close, but when I try to print the sum it isn't working. Here is my code.

void DisplayB(int b[][4], int col, int row, int total);


int main()
{
    int total = 0;

    int b[3][4] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 };

    DisplayB(b, 3, 4, total);


}

void DisplayB(int b[][4], int col, int row, int total)
{
    total = 0;
    cout << "Array c using the display function: " << endl;
    for (int i = 0; i<col; i++)   
    {
        for (int j = 0; j<row; j++) 
        {
            cout << b[i][j] << "  ";

            total+=b[i][j];
        }
            cout<<total;
            cout << endl;

    }

}

When I run this in the compiler I end up getting this:

1 2 3 4 10
5 6 7 8 36
9 10 11 12 78

It looks like what's happening is it finds the sum of the each row and adds it to the sum of the prior row. Any ideas?

Answer 1

Your function is very confusing.

void DisplayB(int b[][4], int col, int row, int total)
{
    total = 0;
    cout << "Array c using the display function: " << endl;
    for (int i = 0; i<col; i++)   
    {
        for (int j = 0; j<row; j++) 
        {
            cout << b[i][j] << "  ";

            total+=b[i][j];
        }
            cout<<total;
            cout << endl;

    }

}

For example the original array has three rows but the corresponding parameter of the function you named like col. And vice versa the number of columns you named like rows in the function declaration.

Also inside the outer loop you output partial sums of the array. For example

1 2 3 4 10
5 6 7 8 36
9 10 11 12 78

10 is the sum of 1, 2, 3, 4. 36 is the sum of 1, 2, 3, 4 and 5, 6, 7, 8 and so on.

I think you want to output the sum after displyaing the array. Take into account that parameter total is redundant. You could simply declare a local variable with name total within the function.

I would separate the function into two functions. One is designed to output the array and other is designed to calculate the sum of all elements of the array.

In this case the program would look like

#include <iostream>
#include <iomanip>

const size_t N = 4;

void DisplayB( const int b[][N], size_t rows )
{
    std::cout << "Array b using the display function:\n" << std::endl;

    for ( size_t i = 0; i < rows; i++ )   
    {
        for ( size_t j = 0; j < N; j++ ) 
        {
            std::cout << std::setw( 2 ) << b[i][j] << ' ';
        }

        std::cout << std::endl;
    }
}

long long int Accumulate( const int b[][N], size_t rows )    
{
    long long int total = 0;

    for ( size_t i = 0; i < rows; i++ )   
    {
        for ( size_t j = 0; j < N; j++ ) 
        {
            total += b[i][j];
        }
    }

    return total;    
}    

int main()
{
    int b[3][N] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 };

    DisplayB( b, 3 );

    std::cout << "\nSum of elements of the array is " 
              << Accumulate( b, 3 ) 
              << std::endl; 
}

The program output is

Array b using the display function:

 1  2  3  4 
 5  6  7  8 
 9 10 11 12 

Sum of elements of the array is 78

Answer 2

void DisplayB(int b[][4], int col, int row, int total)
{
    total = 0;
    cout << "Array c using the display function: " << endl;
    for (int i = 0; i<col; i++)   
    {
        int sub_total = 0;
        for (int j = 0; j<row; j++) 
        {
            cout << b[i][j] << "  ";

            sub_total+=b[i][j];
        }
            total += sub_total;
            cout<<"Sub total "<<sub_total;// Optional
            cout << endl;
    }
    cout<<"Over all total "<<total;

}

Answer 3

#include <iostream>

using std::cout;
using std::endl;

void DisplayB(int b[][4], int row, int col, int total);


int main()
{
    int total = 0;

    int b[3][4] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 };

    DisplayB(b, 3, 4, total);


}

void DisplayB(int b[][4], int row, int col, int total)
{
    total = 0;
    cout << "Array c using the display function: " << endl;
    for (int i = 0; i<row; i++)   
    {
        for (int j = 0; j<col; j++) 
        {
            cout << b[i][j] << "  ";

            total+=b[i][j];   
        }
        //This is for row-wise addition
        //cout<< "\nTotal of row " << i << " is : " << total << endl;
        //total = 0;
        cout << endl;
    }
    cout<<"\nTotal = " << total << endl;
}