Reading Input From File and Storing into 2D Array - c++

Question

I need to read in a text file that contains only integers and each one is separated by new line. example would be:
0
1
2
...
64
repeating 0 to 64 64 times
Essentially the file is 64*64 lines long, containing an integer for each line.
I need to store each integer (line) in ldisk, my 2D array, but am having serious problems doing so. I understand my code has an error because I am trying to store a string in a char, but I am not sure how to get around this. By the way, ldisk must be a 2-D array of chars. I would love some advice/feedback on my current code posted below, or an alternative solution.
NOTE: I am a beginner at C++
PS:
I know similar topics exist, but mine is more to the problem of getting around the type conversion or just converting it properly so I can store more than a single digit integer into my 2D array, because I have it working where I can store only the first digit where I want in my 2D array, but run into problems if there is more than 1 digit.
int main(){
char **ldisk;
ldisk = new char*[64];
for (int i = 0; i<64; i++)
{
ldisk[i]= new char[64];
}
int counter = 0;
string line;
ifstream inFile("example2.txt");
while ( getline(inFile, line))
{
int first, second;
first = counter/64;
second = counter%64;
cout << line;
ldisk[first][second]= line;
}
return 0;
}
EDIT:
My apologies I have no idea how to do a table.
I want ldisk[0][0] to be 0,
then ldisk[0][1] to be 1,
then ldisk[0][2] to be 2,
etc,
etc,
then ldisk[0][63] to be 64
Eventually it will fill up such that ldisk[63][63] = 64

Answer 1

This is the problem:
ldisk[first][second]= line;
The type of ldisk[first][second] is char. You are trying to assign a std::string to it.
You can make your life a lot simpler by using a std::vector<std::string>.
#include <iostream>
#include <fstream>
#include <vector>
#include <string>
using namespace std;
int main(){
vector<string> ldisk;
int counter = 0;
string line;
ifstream inFile("example2.txt");
while ( getline(inFile, line))
{
cout << line;
ldisk.push_back(line);
}
return 0;
}
Update
If you must have char** ldisk, you can change main to:
int main()
{
char **ldisk;
ldisk = new char*[64];
for (int i = 0; i<64; i++)
{
ldisk[i]= new char[64];
}
int counter = 0;
string line;
ifstream inFile("example2.txt");
while ( getline(inFile, line) && counter < 64 )
{
cout << line << endl;
if ( line.size() >= 64 )
{
cout << "Line is longer than 63 characters. Copying only 63 characters from it.\n";
strncpy(ldisk[counter], line.c_str(), 63);
ldisk[counter][63] = '\0';
}
else
{
strcpy(ldisk[counter], line.c_str());
}
++counter;
}
return 0;
}

Answer 2

Change your loop to:
for (counter = 0; counter < 64*64; ++counter)
{
int item;
if ( !(inFile >> item) )
{
cerr << "File only contained " << counter << "items.\n";
return 1;
}
if ( item < CHAR_MIN || item > CHAR_MAX )
{
cerr << "Item " << counter << " invalid value " << item << "\n";
return 2;
}
ldisk[counter/64][counter%64] = item;
}
The missing ingredient is that you were not trying to convert the string in your file into an integer value. You may need #include <climits>.