使用C ++循环钻取的编程原理和实践。 找不到退出循环的方法

Question

I'm going through Bjarne Stroustrup's 'Programming : Principles and Practice using C++" and I've got a drill which tells me to write a program that consists of a while-loop that (each time around the loop) reads in two ints and then prints them and that it should exit when "|" is entered. I've written the program(I'm sure there's a easier way of writing it, but I've got the "gift" of overcomplicating things), but I can't find a way of exiting the loop. Here's the code:

#include <iostream>
#include <vector>

int main()
{

    std::vector<int> answers;
    int answer;
    int intCounter=0;

    while(answers.size()<=2  )
    {

        if(answer=='|')
        {
            return 0;
        }
        std::cin>>answer;
        answers.push_back(answer);
        ++intCounter;

        if(intCounter==2)
        {
            for(int x : answers)
            {
                std::cout<<x<<'\n';
            }
            answers.clear();
            intCounter=0;
        }

    }

    return 0;
}

Basically if I write an if statement to check if answer is equal to '|', the compiler thinks i meant the int value of it(124 or something like that) and terminates the loop when I write 124, and that's clearly not what I want. I've tried to look over the internet for a way of converting an int into a char, but I haven't understood anything from there. The simplest solution would be the best.

Answer 1

cin >> answer will fail when the next non-whitespace character to be read is not a number. You can use that behavior to end the loop.

// Break inside the loop.
while( true  )
{
    std::cin>>answer;

    // If there was an error in reading, break out of the loop.
    if ( !std::cin )
       break;

    answers.push_back(answer);

    ++intCounter;

    if(intCounter==2)
    {
        for(int x : answers)
        {
            std::cout<<x<<'\n';
        }
        answers.clear();
        intCounter=0;
    }
}

Answer 2

Two changes:

1. If your task is to just print numbers you could just use string.

2. You are checking value of answer to | before its even been input. So

    #include<iostream> #include <vector> #include<string> using namespace std; int main(){ std::vector<string> answers; string answer; int intCounter=0; while(answers.size()<=2 ){ std::cin>>answer; //after input if(answer=="|"){ return 0; } answers.push_back(answer); ++intCounter; if(intCounter==2){ for(int x=0;x< answers.size();x++){ std::cout<<answers[x]<<'\\n'; } answers.clear(); intCounter=0; } } return 0; }