Read everything up to a whitespace from a text file - c++

Question

(C++) I've created a function to open the text file and assign the contents to an array. The first 2 elements in the array are the size of the grid. However, if either or both of the first 2 numbers are double digits, it doesnt read them in as double digits. Is there any way of doing this?
int openMap()
{
std::string fileName;
std::cout << "Please enter the file name with extension that you want to open: ";
std::cin >> fileName;
system("CLS");
std::ifstream file(fileName); //OPENS MAP FILE
int tmp;
int i = 0;
if (!file.is_open()) //CHECKS IF THE MAP FILE HAS OPENED CORRECTLY
{
std::cout << "Error Occured!\nCould not open file.";
return 0;
}
while (!file.eof()) //READS THE MAP FILE AND PASSES THE INFORMATION INTO AN ARRAY
{
file >> tmp;
checkNumber(tmp);
if (valid == true) //IF THE CHARACTER IS NOT A NUMBER THEN IT WONT BE PASSED INTO THE ARRAY
{
tmpArray[i] = tmp;
i++;
valid = false;
}
row = tmpArray[1]; //ASSIGNS THE FIRST 2 NUMBERS OF THE MAP FILE TO ROW AND COL VARIABLES
col = tmpArray[0];
}
return row, col;
}
I would assume I have to rewrite
file >> tmp
in some sort of different way, but not sure how.
Is there a way to scan through the text file until it hits a whitespace?
The text file contents looks like this
6 4 0 0 1 0 0 0 2 0 1 0 1 1 0 0 1 0 0 0 0 0 0 0 3 0
(the 6 or 4 or both can be double digits instead)
Edit:
for (int j = 0; j < row; j++)
{
for (int k = 0; k < col; k++)
{
_map[j][k] = tmpArray[l];
std::cout << _map[j][k] << " ";
l++;
}
}

Answer 1

There's quite a number of bugs in the code, you should probably use a debugger to step through and identify which parts of your program don't behave as expected.
while(!file.eof())
file >> tmp;
checkNumber(tmp);
if (valid == true) //IF THE CHARACTER IS NOT A NUMBER THEN IT WONT BE PASSED INTO THE ARRAY
{
tmpArray[i] = tmp;
i++;
valid = false;
}
row = tmpArray[1]; //ASSIGNS THE FIRST 2 NUMBERS OF THE MAP FILE TO ROW AND COL VARIABLES
col = tmpArray[0];
You set row=tmpArray[1] and col = tmpArray[0] every iteration of the loop which is not only unnecessary but also incorrect, especially since row=tmpArray[1] is being executed at i=0 when nothing has been placed in tmpArray[1] yet.
EDIT: This is a lot smaller, less error prone due to less variables and type conversions, and easier to read:
int row,col;
//Add error checking here
cin >> col;
cin >> row;
cout << "Cols: " << col << " Rows: " << row << endl;
vector<vector<int> >_map(row, vector<int>(col,0));
for(int j=0; j < row; j++)
{
for(int k=0; k < col; k++)
{
int tmp;
cin >> tmp;
//Add error checking for tmp
_map[j][k] = tmp;
cout << _map[j][k] << endl;
}
}

Answer 2

There are some problems with your code. First the return type of your function is int but you are returning multiple values. Here is a complete running code which should solve your problem.
#include <iostream>
#include <fstream>
#include <vector>
std::vector< std::vector<int> > openMap() {
std::string fileName;
std::cout << "Please enter the file name with extension that you want to open: ";
std::cin >> fileName;
std::fstream myfile(fileName, std::ios_base::in);
int row, col;
myfile >> row;
myfile >> col;
int a;
std::vector< std::vector<int> > retval;
for (int i = 0; i < row; i++) {
std::vector<int> v1;
for (int j = 0; j < col; j++) {
myfile >> a;
v1.push_back(a);
}
retval.push_back(v1);
}
return retval;
}
int main(int argc, char * argv[])
{
std::vector< std::vector<int> > _map = openMap();
for(int i = 0; i < _map.size(); i++) {
for (int j = 0; j < _map[i].size(); j++) {
std::cout << _map[i][j] << " ";
}
std::cout << std::endl;
}
return 0;
}

Answer 3

I guess that not so many people will be interested. But please see below a possible solution to your problem.
The code uses modern C++ algorithms.
It is very simple and straightforward.
#include <iostream>
#include <fstream>
#include <vector>
#include <iterator>
#include <algorithm>
int main() {
// Ask user, to give a filename
std::cout << "Please enter the file name with extension that you want to open: ";
// Get the filename from the user
if (std::string fileName; std::cin >> fileName) {
// Open the file and check, if it is open
if (std::ifstream sourceFile(fileName); sourceFile) {
// Read the number of rows and columns of the matrix
if (size_t numberOfColumns, numberOfRows; sourceFile >> numberOfColumns >> numberOfRows) {
// Create a matrix with the given number of rows and columns
std::vector<std::vector<int>> result(numberOfRows, std::vector<int>(numberOfColumns, 0));
// Read data from the input stream and put it into the matrix
for (size_t i = 0; i < numberOfRows; ++i) {
std::copy_n(std::istream_iterator<int>(sourceFile), numberOfColumns, result[i].begin());
}
// Print result. Go through all lines and then copy line elements to std::cout
std::for_each(result.begin(), result.end(), [](std::vector<int>& c) {
std::copy(c.begin(), c.end(), std::ostream_iterator<int>(std::cout, " ")); std::cout << "\n"; });
}
}
else {
std::cerr << "\n*** Error: Could not open source File\n\n";
}
}
return 0;
}