Question

Is it possible to read alphanumeric characters only from the given input line ignoring everything else in C/C++? I am trying to read whole line at a time.

Suppose we have to read the line:

 aaa, bbb, ccc .

Here, my intention is to ignore comma, dot and space while taking input.

Answer 1

You can do this in several ways, for example the simplest is to read the whole line and then remove the bits you don’t want later:

#include <algorithm>
#include <iostream>
#include <string>
#include <functional>
#include <ctype.h>

int main() {
  std::string line;
  while (std::getline(std::cin, line)) {
    line.erase(std::remove_if(line.begin(), line.end(), std::not1(std::ptr_fun(isalnum))), line.end());
    std::cout << line << "\n";
  }
}

Reads a line and then removes any characters which return false for isalnum. (In C++11 you can simplify this slightly)