C++ 时间限制不起作用

Question

如果用户在几秒钟内没有输入，我有这个程序应该结束并打印一条消息。但是现在时间限制似乎不起作用，尽管我的代码看起来合乎逻辑。 (如果用户没有输入任何内容，时间不会消失)这是为什么？

int userInput = 0;
int now = time(0);
int later = 0;
int elapsed = 0;
do {
    later = time(0);
    elapsed = later - now;
    cout << "Enter number" <<endl;
    cin >> userInput;   
    switch (userInput)
    {
        case 1: 
         elapsed = 0;
         break; 
    }

} while (elapsed < 4 && !_kbhit()); 


if (elapsed == 4)
{
    system("cls");
    cout << "Too Slow!! Now You're on the Menu!";
    return 0;
}

Answer 1

不提供保证，但如果使用 kbhit 是解决方案的一部分，那么您可能只想在检测到某些键盘事件时尝试阅读。

int userInput = 0;
int now = time(0);
int later = 0;
int elapsed = 0;

cout << "Enter number" <<endl;

do {
    later = time(0);
    elapsed = later - now;
    if(_kbhit()) { // we **may** have some input
        cin >> userInput;
        // this is useless for timing purposes!!
        // A simple `break` should suffice.
        switch(userInput)
        {
           case 1: 
             elapsed = 0;
           break; 
        }
    }

} while (elapsed < 4); 


if (elapsed == 4)
{
    system("cls");
    cout << "Too Slow!! Now You're on the Menu!";
    return 0;
}