CODEWITHSUNDEEP
c++
Russell
Russell

Reputation: 23

How do I know when one is done entering cin with \n? (loop)

From Australian voting problem:

A bot will keep putting information and it can reach 1000 lines. Example of what he'll enter:

"1 2 3
2 1 3
2 3 1
1 2 3
3 1 2
"

How do I know when he has finished entering information? There is an extra \n at the end and that's my only guess on where to go. cin doesn't seem to detect \n, but getchar() apparently does. It will however get the \n even after the first line of course, and getting it to work has become rather difficult. How do I accomplish this?

Upvotes: 0

Views: 310

Answers (4)

JoshD
JoshD

Reputation: 12824

I'd suggest using cin.getline It will get a whole line at a time (ending with \n) and when you get an empty line, you know you're done.

Edit As suggested by sbi, std::getline is typically a better option for this situation as it utilizes strings rather than char arrays.

Upvotes: 6

sbi
sbi

Reputation: 224179

std::string line;
while( std::getline(std::cin,line) && !line.empty() ) {
  std::istringstream iss(line);
  int i1, i2, i3;
  iss >> i1 >> i2 >> i3
  if( !is ) throw "dammit!"
  process_numbers(i1,i2,i3);
}
if( !std::cin.good() && !std::cin.eof() ) throw "dammit!";

Upvotes: 3

Amber
Amber

Reputation: 527388

You could instead read a line at a time, and look for the blank line (then later splitting each non-blank line into its 3 numbers).

Upvotes: 0

Greg Hewgill
Greg Hewgill

Reputation: 994669

Reading input with cin and the extraction operator >> skips whitespace. Instead, read the input line by line and exit when the line is empty.

Upvotes: 1

Related Questions