istream_iterator + double vector

[nishika]

Meet the problem when the flow-through elements are introduced istream_operator<int>♪ Knowledge comes more than necessary.

If there's any advice on improving the quality of the code, I'll just be grateful. Here's the code:

#include <iostream>
#include <vector>
#include <iterator>
#include <algorithm>
using namespace std;
int main() {
vector<vector<int>> price;

unsigned int n = 0;

cin>>n;

price.reserve(n);

for (int i = 0 ; i < n;   i++)

{

vector<int> vec(2,0);

price.push_back(vec);

}

for (int i = 0; i < n ; i++)

{

for (int j = 0; j < 2;j++)

{

istream_iterator<int> in(cin);

price[i][j] = *in;

++in;

}

}

for (int i = 0; i < n ; i++)

{

ostream_iterator<int> out(cout," ");

for (int j = 0; j < 2;j++)

{

copy(price[i].begin(),price[i].begin()+n,out);

}

}

return 0;

}

[Analeea]

You have this cycle.

  for (int i = 0; i < n ; i++)
  {
    ostream_iterator<int> out(cout," ");
     for (int j = 0; j < 2;j++)
     {
       copy(price[i].begin(),price[i].begin()+n,out);    
     }
   }

Uncorrect.

That's right.

  for ( int i = 0; i < n ; i++)
  {
    ostream_iterator<int> out( cout, " " );
    copy( price[i].begin(), price[i].end(), out );    
  }

Or

  ostream_iterator<int> out( cout, " " );
  for ( int i = 0; i < n ; i++)
  {
    copy( price[i].begin(), price[i].end(), out );    
  }

Or

  ostream_iterator<int> out( cout, " " );
  for ( vector<vector<int>>::size_type i = 0; i < price.size() ; i++)
  {
    copy( price[i].begin(), price[i].end(), out );    
  }

You mean you're all in the same line, not in the form of a matrix.

It would be easier to write.

for ( const auto &row : price )
{
    for ( auto x : row ) std::cout << x << ' ';
    std::cout << std::endl;
}

But it looks like you want to practice with the terator. :

Also instead of this fragment, the code

 vector<vector<int>> price;
  unsigned int n = 0;
  cin>>n;
  price.reserve(n);
  for (int i = 0 ; i < n;   i++)
  {
    vector<int> vec(2,0);
    price.push_back(vec);
  }

You could write that down.

  unsigned int n = 0;
  cin>>n;
vector<vector<int>> price( n, vector<int>( 2 ) );

In these cycles, the definition of the inlet may be outwards.

   istream_iterator<int> in(cin);

for (int i = 0; i < n ; i++)

{

for (int j = 0; j < 2;j++)

{

price[i][j] = *in;

++in;

}

}

Of course it would be easier not to use the terator, but to write it simply.

for (int i = 0; i < n ; i++)

{

for (int j = 0; j < 2;j++)

{

cin >> price[i][j];

}

}