How to separate data from getline each time there is a space - c++

Question

int main() {
ifstream billFile;
billFile.open("bill.in"); //opening file
if( billFile.is_open() ){
string line1;
getline(billFile, line1);
cout << line1 << endl;
}
The bill.in file contains:
12 100
How can I separate 12 and 100 into two different variables?

Answer 1

You can use std::istringstream to parse line1:
int main()
{
ifstream billFile("bill.in"); //opening file
if( billFile.is_open() )
{
string line1;
if( getline(billFile, line1) )
{
istringstream iss(line1);
int value1, value2;
if( iss >> value1 >> value2 )
cout << value1 << ' ' << value2 << endl;
}
}
}
Of course, if your file has only 1 line, then you can just omit getline(), eg:
int main()
{
ifstream billFile("bill.in"); //opening file
if( billFile.is_open() )
{
int value1, value2;
if( billFile >> value1 >> value2 )
cout << value1 << ' ' << value2 << endl;
}
}

Answer 2

I use the following split function to divvy up each line based on some set of delimiters (a space in your case).
std::vector<std::string> split(const std::string& str,
std::string delims = " \t") {
std::vector<std::string> strings;
size_t start;
size_t end = 0;
while ((start = str.find_first_not_of(delims, end)) != std::string::npos) {
end = str.find_first_of(delims, start);
strings.push_back(str.substr(start, end - start));
}
return strings;
}
then you can split each line into a vector of strings:
int main() {
ifstream billFile;
billFile.open("bill.in"); //opening file
if( billFile.is_open() ){
string line;
getline(billFile, line);
std::vector<std::string> str = split(line, " ");
std::string line1 = str[0];
cout << line1 << endl;
}
}
You use this method to split up strings using any delimiter you want.

Answer 3

If you input file only contains one line and your keyboard is in very poor working order and you really need to minimize keystrokes you can write:
int main(){
int v1, v2;
if(std::ifstream("bill.in") >> v1 >> v2){
// here you have valid v1 and v2.
}
}
The >> "formatted input" is appropriate here because it is convenient to understand the contents of the text file as numbers.

Answer 4

Function std::getline() takes delimitation as claimed in C++ reference. So just use getline(istream, str, ' ');.
Modify your codes as
int main() {
ifstream billFile;
billFile.open("bill.in"); //opening file
if( billFile.is_open() ){
string line1;
getline(billFile, line1, ' ');
cout << line1 << endl;
}