I have got some problems with adding up numbers from a .txt file

Question

I got a homework in school and I have done it but the result is not exactly what I wanted.

The task is to get sums from a text file with the following rules:

the first column contains numbers
the second is a 0/1 boolean (the separating character is space)
whenever the bool is true in continuous lines, the programme should add up the numbers

The .txt file looks like this:

Input:

20 1

30 1

40 0

50 1

60 1

Desired Output:

50

110

Code:

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main()
{
string line;
double number;
double sum;
int boolean;
sum = 0;

ifstream homework;
homework.open("homework.txt");
    while (!homework.eof())
    {
        homework >> number >> boolean;

        if (boolean == 1)
        {
            sum += number;          
        }
    }

cout << sum << endl;

homework.close();

system("pause");
return 0;
}

I wanted the code to print out 50 and 110 (because there is a line with a false boolean) but instead, the code printed 160 (so it summed up all lines with true boolean).

Any ideas?

First of all, when you create a [Minimal, Complete, and Verifiable Example](http://stackoverflow.com/help/mcve) make sure it doesn't contain any unrelated errors (yours do). Then also please read [Why is iostream::eof inside a loop condition considered wrong?](https://stackoverflow.com/questions/5605125/why-is-iostreameof-inside-a-loop-condition-considered-wrong) — Some programmer dude, Aug 07 '17 at 13:18
your "boolean" var don't seam to be declared anywhere, I'm suprised your code would compile at all. — Remy Grandin, Aug 07 '17 at 13:22

Tommy Andersen · Accepted Answer · 2017-08-07T13:24:58.947

3

The problem is that you do not output until the file has been iterated completely, so you see the total sum, and not the sum after each false boolean value. If you want sub totals every time you encounter a boolean false you need to add something to your loop:

while (homework >> number >> boolean)
{
    if (boolean)
    {
        sum += number;          
    }
    else
    {
        cout << sum << endl;
        sum = 0;
    }
}

Btw. how is your boolean variable boolean declared, does your code even compile? I have changed the check in my sample (removed the == 1).

edited Aug 07 '17 at 13:24

answered Aug 07 '17 at 13:19

Tommy Andersen

7,165
1
31
50

Oh yeah, I forgot to write it in. Besides that, it worked fine. – introvertbustardxd Aug 07 '17 at 13:24

score 0 · Answer 2 · answered Aug 07 '17 at 13:20

0

You need to put the line cout << sum << endl; in an else case inside the while loop, as well as reset the sum.

Something like this should do:

while (!homework.eof())
{
    homework >> number >> boolean;

    if (boolean == 1)
    {
        sum += number;          
    }
    else
    {
        cout << sum << endl;
        sum = 0;
    }
}

answered Aug 07 '17 at 13:20

katrinamo

1
1

Even better: `std::cout << sum << `'\n'`;`. You don't need the extra stuff that `std::endl` does. – Pete Becker Aug 07 '17 at 13:28

ΦXocę 웃 Пepeúpa ツ · Answer 3 · 2017-08-07T13:30:33.340

0

You have many choices, one could be:

1st one: define the boolean variable as exactly that (a bool variable) and compare those against a true false

example:

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main()
{
    string line;
    bool boolean;
    double number{ 0 };
    double sum{ 0 };

    ifstream homework;
    homework.open("hw.txt");
    while (!homework.eof())
    {
        homework >> number >> boolean;

        if (boolean)
        {
            sum += number;
        }
    }
    cout << sum << endl;
    homework.close();

    return 0;
}

to stop the while when a false is found you can use a break

    if (boolean)
    {
        sum += number;
    }
    else {
        break;
    }

edited Aug 07 '17 at 13:30

answered Aug 07 '17 at 13:25

ΦXocę 웃 Пepeúpa ツ

47,427
17
69
97

What would he benefit from using a string? an integer is faster, and he already has it, why should he change it to a string? – Tommy Andersen Aug 07 '17 at 13:27
1

Ok, but still none of your proposals fixes the problem the OP has, which is showing the total after each time a false value occurs. :) – Tommy Andersen Aug 07 '17 at 13:29

I have got some problems with adding up numbers from a .txt file

3 Answers3