Seokho Song
Seokho Song
1 min read




  • English
  • 한국어(번역 준비중)

Today, I’ve started an algorithm study.

I’ve learned something didn’t know before.

Today’s problem is this:


Write a program printing sum of A and B which are inputted.


Input values consist of multiple test-case. 
Each test-case is a single line and will be given value A and B (0 < A, B<10)


Print A + B by each test-case.

Example input

1 1
2 3
3 4
9 8
5 2

Example output


From here.

So, Let’s think about it.

When I met this problem, I’m just shocked.

Honestly, I have no idea for solving this problem.

Because this problem didn’t have information about the limitation of input.

So I try to find how can I solve this problem on Google and an answer sheet.

And I got Idea.

An Eof.

This fact makes me a little bit annoying because I can’t find any information about Eof in that judgment site.

So this problem’s solution is this.

#include <iostream>

using namespace std;
int main()
    int a, b;
    while(cin >> a >> b)
        cout << a + b << endl;
    return 0;

The answer has a quite funny fact.

The » operator that was overridden return istream itself.

That makes possible we can write like this.

	cin >> a >> b;

Did you find anything weird?

operator » have been used the condition of the while loop.

From reference, We can find the return value of overridden bool operation that is selected by an error state of ios_base::iostate flag.

So If the state value of ‘cin’ is eof, we can escape from the while loop.

I didn’t know istream’s functions before, so this problem gave me the knowledge and it’s quite happy :D.