Reading a file of two columns into one array

Question

I have a very basic question. I'm trying to read from a file that has data saved like this:

Collins, Bill
Smith, Bart
Allen, Jim
.
.
.
Holland, Beth

and I would like my code to read the data and save them into one column of an array. So what I did was,

#include<iostream>
#include<string>
#include<cstring>
#include<iomanip>
#include<fstream>

using namespace std;

int main()
{
string first, last, FIRST[200], LAST[200];

ifstream infile;
infile.open("names.dat");

while (!infile.eof())
{
for (int i = 0; i < !infile.eof(); i++)
{
    infile >> first;
    FIRST[i] = first;
    cout << FIRST[i] << " ";

    infile >> last;
    LAST[i] = last;
    cout << LAST[i] << " " << endl;
    }
}
return 0;
}

However, I want just one array named NAME[], not two(FIRST[] & LAST[]). So basically if I call NAME[0] would be Collins, Bill.

I really don't know how to do this... reading sources makes me even more confused..

This is just a little part of the entire program that I have to write, which is sorting names alphabetically and I haven't even passed this stage yet.

So, why don't you use one 2D array then with proper indexing? — László Papp
– László Papp, Commented Apr 6, 2014 at 5:41
@DieterLücking cuz I thought I needed to do i < infile.eof() instead of !infile.eof() but it didn't work... this code at least worked so.. — weathergirl
– weathergirl, Commented Apr 6, 2014 at 5:46

score 2 · Accepted Answer · 2014-04-06 06:06:39Z

2

You might just read each line:

#include<iostream>
#include<fstream>
#include<deque>

int main()
{
    std::deque<std::string> names;
    std::ifstream infile("names.dat");
    std::string name;
    while(getline(infile, name))
        names.push_back(name);
    return 0;
}

Testing for EOF is often not a test for a successful input. Here the getline returns the stream and the condition while(stream) is testing the stream state.

Regarding the comment:

Have a #include<algorithm> and std::sort(names.begin(), names.end());

edited Apr 6, 2014 at 6:06

answered Apr 6, 2014 at 5:53

user2249683

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4 Comments

László Papp Over a year ago

The OP wanted to read the data into an array, so this does not answer the question.

weathergirl Over a year ago

the reason why i wanted an array is that I have to eventually write a code that will sort the names alphabetically and thought an array will be easier

László Papp Over a year ago

@weathergirl: you can sort an array with std::sort as well as some other containers.

weathergirl Over a year ago

@DieterLucking I tried your method and it gives me bunch of errors. I don't know what is wrong, since I haven't used deque ever yet.

R Sahu · Accepted Answer · 2014-04-06 05:52:23Z

1

Just use one array of strings instead of two.

int main()
{
   string first, last, NAME[200];

   ifstream infile;
   infile.open("names.dat");
   int i = 0;

   while (true)
   {
      infile >> first;
      infile >> last;

      if (!infile.eof() && infile.good() )
      {
         NAME[i] = last + ", " + first;
         cout << NAME[i] << std::endl;
      }
      else
      {
         break;
      }
      ++i;
   }
   return 0;
}

edited Apr 6, 2014 at 5:52

answered Apr 6, 2014 at 5:46

R Sahu

207k15 gold badges168 silver badges291 bronze badges

1 Comment

László Papp Over a year ago

Actually, the OP's code is invalid, and I would not suggest to copy and paste that further on. Please also see the comments.

László Papp · Accepted Answer · 2014-04-06 05:55:09Z

1

Just use a 2D dimensional array then as follows:

main.cpp

#include<iostream>
#include<string>
#include<cstring>
#include<iomanip>
#include<fstream>

using namespace std;

int main()
{
    string first, last, myarray[200][2];

    ifstream infile;
    infile.open("names.dat");

    int i = 0;
    while (!infile.eof()) {
        infile >> first;
        myarray[i][0] = first;
        cout << myarray[i][0] << " ";

        if (infile.eof()) {
            cout << endl;
            break;
        }

        infile >> last;
        myarray[i][1] = last;
        cout << myarray[i][1] << " " << endl;
        ++i;
    }
    return 0;
}

Output

Collins, Bill
Smith, Bart
Allen, Jim

That being said, I would personally use std::array or some more intelligent container type in C++, in general.

edited Apr 6, 2014 at 5:55

answered Apr 6, 2014 at 5:45

László Papp

53.5k40 gold badges118 silver badges142 bronze badges

1 Comment

weathergirl Over a year ago

Quick question here, would mixing pre/post increment of i here make any difference??

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