This vector assignment is too general, please help!

[Mandory22]

Original assignment :

Given a file with a random number of lines and each line consists of a random number of integers.

For example :

155 779 588
883 974 789 9533
345 534

Store all numbers in each line into a vector of integers. Then you print out the contents of the vectors.

Expected output :
Vector 1 :
155, 779, 588

Vector 2 :
883, 974, 789, 9533

Vector 3 :
345, 534

Another example :

255 999 755 143 633 247
884 335
993 566 100 633
124 755 332 624 825

Expected output :
Vector 1 :
255, 999, 755, 143, 633, 247

Vector 2 :
884, 335

Vector 3 :
993, 566, 100, 633

Vector 4 :
124, 755, 332, 624, 825

Please note that the number of lines may be unlimited and the number of integers for each line may be also unlimited.

I currently have no idea how to approach it. Could you please give me some general idea so that as to help me implement my solution? Thank you very much.

[gunnerfunner]

create a std::vector<std::vector<int>> as the holding container
read the file one line at a time with getline into a std::string object
create a std::istringstream object with the the std::string object from above
while reading the std::istringstream object into a dummy int push_back the int into a std::vector<int>
if the file is open push_back this std::vector<int> into the holding container

[Mandory22]

I have tried it, but I repeatedly fail and don't know where to start.

#include <iostream>
#include <fstream>
#include <vector>
#include <sstream>
using namespace std;
int main ()
{
stringstream ss;
string str;
vector < vector < int > > vect_numbers;
int numbers;
ifstream file_reader( "numbers.txt" );
if ( ! file_reader.is_open() )
{
cout << "Can't open file!\n";
}
else
{
while ( file_reader )
{
if ( ! getline( file_reader, str, '\n' ) )
{
break;
}
ss << str;
while ( ss >> numbers )
{
vect_numbers.resize( vect_numbers.size() + 1 );
vect_numbers.back().push_back( numbers );
ss.clear();
}
}
for ( int i = 0; i < vect_numbers.size(); i++ )
{
cout << "Vector " << i + 1 <<":\n";
for ( int j = 0; j < vect_numbers[ i ].size(); j++ )
{
cout << vect_numbers[ i ][ j ] << " ";
}
cout << endl;
}
}
file_reader.close();
cin.get();
}

With :

255 999 755 143 633 247
884 335
993 566 100 633
124 755 332 624 825

The program only outputs the first line, but each number is a vector! What is wrong here?

[Thomas1965]

For each line you read you need to create another vector and insert it in the outer vector:

#include <iostream>
#include <fstream>
#include <vector>
#include <sstream>

using namespace std;

int main()
{
  string str;
  vector < vector < int > > vect_numbers;
  int numbers;
  ifstream file_reader("numbers.txt");
  if (!file_reader.is_open())
  {
    cout << "Can't open file!\n";
  }
  else
  {
    while (getline(file_reader, str))
    {
      istringstream ss(str);
      vector<int> tmp;
      while (ss >> numbers)
      {
        tmp.push_back(numbers);
      }
      vect_numbers.push_back(tmp);
    }
    int i = 0;
    for (auto v: vect_numbers)
    {
      cout << "Vector " << i + 1 << ":\n";
      for (auto num : v)
      {
        cout << num << "\t";
      }
      cout << "\n";
      i++;
    }
  }
  cin.get();
}

OUTPUT:

Vector 1:
255 999 755 143 633 247
Vector 2:
884 335
Vector 3:
993 566 100 633
Vector 4:
124 755 332 624 825

[gunnerfunner]

if the file is open push_back this std::vector<int> into the holding container

I'd probably stick in a if(file_reader){} loop around vect_numbers.push_back(tmp) to make sure that we get predictable results (cf: discussion with Chervil on this couple days back: http://www.cplusplus.com/forum/beginner/206784/)
And std::string str might well be declared within the else loop in keeping with the principle of declaring variables as locally scoped as possible: http://stackoverflow.com/questions/3773396/declare-variables-at-top-of-function-or-in-separate-scopes

[Mandory22]

Thanks all. Because of all of you I was able to complete this assignment :)