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c++ - 为什么循环是无限的？

问题描述

我正在做一些功课并试图使其免受字符输入的影响，但不知何故在里面写一个字符仍然会破坏它，因为它会使循环无限。任何人都可以提出解决方法吗？这是代码：

#include <iostream>
#include <cstdlib>
#include <ctime>
int main()
{
    srand( time( NULL ) );

    int given = 0;
    int imaginarynum = ( std::rand() % 99 ) + 1;
    int tries = 0;

    std::cout << "Hello! We'regoing to play an easy game! I'm goinng to think of a number between 1-100 and you'll have to guess it! " << std::endl;
    std::cout << given << " "<< imaginarynum;

    while(given < imaginarynum || given > imaginarynum)
    {
        std::cin >> given;
        bool error = std::cin.fail();
        std::cin.clear();
        std::cin.sync();

        while(error != false)
        {
            std::cout << "That's not a number!" << std::endl;
            std::cin >> given;
            bool error = std::cin.fail();
            std::cin.clear();
        }

        if (given < imaginarynum)
        {
            std::cout << "I thought of a bigger number! " << std::endl;
            std::cout << "Guess again!" << std::endl;
            tries = tries + 1;
        }else if (given > imaginarynum)
        {
            std::cout << "I thought of a smaller number! " << std::endl;
            std::cout << "Guess again!" << std::endl;
            tries = tries + 1;
        }
        else
        {`enter code here`
            tries = tries + 1;
            std::cout << "Good job! " << std::endl << "It took you: " << tries << " Tries!";
        }
    }

    return 0;
}

标签： c++loopswhile-loopinputstreaminfinite-loop

解决方案

问题是您正在使用两个变量error

    while(error != false)
    {
        std::cout << "That's not a number!" << std::endl;
        std::cin >> given;
        bool error = std::cin.fail();
        std::cin.clear();
    }

在循环中，您声明了一个新变量。用声明替换赋值语句

    while(error != false)
    {
        std::cout << "That's not a number!" << std::endl;
        std::cin >> given;
        error = std::cin.fail();
        std::cin.clear();
    }

第二个问题是您需要清除缓冲区。例如

#include <limits>

//...

std::cin.ignore( std::numeric_limits<std::streamsize>::max(), '\n' );

循环将如下所示

    #include <limits>

    //...

    while(error != false)
    {
        std::cout << "That's not a number!" << std::endl;
        std::cin >> given;
        error = std::cin.fail();
        std::cin.clear();
        std::cin.ignore( std::numeric_limits<std::streamsize>::max(), '\n' );
    }

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