c++ ifstream end of line - c++

Question

I have a file that looks like this:
e r g d g d
f h d r h f
..........
And I want to store these characters in a two-dimensional array
#include <fstream>
#include <iostream>
using namespace std;
int main()
{
ifstream file("file.txt");
char c[20][20];
int i = 0, j = 0;
while(!file.eof())
{
while(!end of line?)
{
file >> c[i][j];
j++;
}
i++;
}
.....
}
how do i do this?
or how to find number of characters in a line?

Answer 1

You can't use eof() like you do. You have to perform an I/O read operation before you can then use eof().
For what you are attempting, you should use std::getline() instead, eg:
#include <iostream>
#include <string>
#include <sstream>
#include <fstream>
#include <algorithm>
int main()
{
std::ifstream file("file.txt");
std::string line;
char c[20][20] = {};
for (int i = 0; i < 20; ++i)
{
if (!std::getline(file, line))
break;
std::istringstream iss(line);
for(j = 0; j < 20; ++j)
{
if (!(iss >> c[i][j]))
break;
}
}
...
return 0;
}
That being said, you should consider using std::vector instead of fixed-sized arrays (unless you know for a fact that your file will never exceed 20 lines and/or 20 characters per line):
#include <iostream>
#include <string>
#include <sstream>
#include <fstream>
#include <iterator>
#include <algorithm>
#include <vector>
int main()
{
std::ifstream file("file.txt");
std::vector<std::vector<char> > c;
std::string line;
while (std::getline(file, line))
{
std::istringstream iss(line);
std::vector<char> tmp;
std::copy(
std::istream_iterator<char>(iss),
std::istream_iterator<char>(),
std::back_inserter(tmp)
);
/* which is equivalent to:
char ch;
while (iss >> ch) {
tmp.push_back(ch);
}
*/
c.push_back(tmp);
}
...
return 0;
}
Alternatively:
#include <iostream>
#include <string>
#include <sstream>
#include <fstream>
#include <iterator>
#include <algorithm>
#include <vector>
typedef std::vector<char> CharVector;
std::istream& operator>>(std::istream &in, CharVector &out)
{
out.clear();
std::string line;
if (std::getline(in, line))
{
std::istringstream iss(line);
std::copy(
std::istream_iterator<char>(iss),
std::istream_iterator<char>(),
std::back_inserter(out)
);
/* which is equivalent to:
char ch;
while (iss >> ch) {
out.push_back(ch);
}
*/
}
return in;
}
int main()
{
std::ifstream file("file.txt");
std::vector<CharVector> c;
std::copy(
std::istream_iterator<CharVector>(file),
std::istream_iterator<CharVector>(),
std::back_inserter(c)
);
/* which is equivalent to:
CharVector cv;
while (file >> cv) {
c.push_back(cv);
}
*/
...
return 0;
}