While 循环不断打印出来，而不是读取下一行答案

【问题标题】：While loop keeps printing out and not reading the next lineWhile 循环不断打印出来，而不是读取下一行
【发布时间】：2015-06-03 18:46:20
【问题描述】：

这是我的第一个简单程序。它不停地打印出Guess what it is.，甚至不要求用户输入。（下一行代码。）我的错误是什么？

 #include <iostream>
 #include <string>
 using namespace std;

int main()
{
    string userName;
    cout << "Hello there.\n";
    cout << "My name is TARS. \n";
    cout << "What is your name? \n";
    getline(std::cin, userName);
    cout << userName << ", let's play a game.\n";
    int secretNum;
    secretNum = rand() % 20 + 1;
    cout << "I'm thinking of a number between 1-20.\n";
    int Guess;
    bool conti = true;

    while (conti)

        cout << "Guess what it is. \n";
        cin >> Guess;   

        if (Guess == secretNum)
        {
            cout << "You read my mind!";
            conti = false;
        }
        if (Guess < secretNum)
        {
            cout << "That is too low.";
        }
        if (Guess > secretNum)
        {
            cout << "That is too high.";
        }

    return 0;
}

【问题讨论】：

把应该重复的代码放在花括号中。您的 while 循环仅假定 while (conti) 之后的第一行应该重复，因为您没有告诉它任何不同。
这些反对票有点不公平。 OP说这是他的第一个程序。做个好人……记住你是怎么开始的……

标签： c++ printing while-loop

【解决方案1】：

你需要使用brackets

#include <iostream>
#include <string>
using namespace std;

int main()
{

    string userName;
    cout << "Hello there.\n";
    cout << "My name is TARS. \n";
    cout << "What is your name? \n";
    getline(std::cin, userName);
    cout << userName << ", let's play a game.\n";
    int secretNum;
    secretNum = rand() % 20 + 1;
    cout << "I'm thinking of a number between 1-20.\n";
    int Guess;
    bool conti = true;

    while (conti)
    {

         cout << "Guess what it is. \n";
         cin >> Guess;

         if (Guess == secretNum)
         {
             cout << "You read my mind!";
             conti = false;
         }

         if (Guess < secretNum)
         {
             cout << "That is too low.";
         }

         if (Guess > secretNum)
         {
             cout << "That is too high.";
         }

    }

    return 0;

}

默认情况下，如果您不使用它们，则只有下一行将被视为 while 循环的一部分在你的情况下：

while (conti)
    cout << "Guess what it is. \n";

【讨论】：

【解决方案2】：

while 循环需要大括号，否则它将永远只执行那条语句。

【讨论】：

【解决方案3】：

while (conti)
cout << "Guess what it is. \n";

相当于：

while (conti)
{
   cout << "Guess what it is. \n";
}

即循环到此结束。您需要的是在正确的位置为循环提供左大括号和右大括号。

while (conti)
{
   cout << "Guess what it is. \n";
   cin >> Guess;
   if (Guess == secretNum)
   {
       cout << "You read my mind!";
       conti = false;
   }
   if (Guess < secretNum)
   {
       cout << "That is too low.";
   }
   if (Guess > secretNum)
   {
       cout << "That is too high.";
   }
}

【讨论】：

【解决方案4】：

你有missed the braces for while 循环。你可以试试这个：

#include <iostream>
#include <string>
using namespace std;

int main()
{

    string userName;

    cout << "Hello there.\n";
    cout << "My name is TARS. \n";
    cout << "What is your name? \n";
    getline(std::cin, userName);
    cout << userName << ", let's play a game.\n";

    int secretNum;
    secretNum = rand() % 20 + 1;

    cout << "I'm thinking of a number between 1-20.\n";

    int Guess;
    bool conti = true;

    while (conti){

        cout << "Guess what it is. \n";
        cin >> Guess;

        if (Guess == secretNum)
        {
            cout << "You read my mind!";
            conti = false;
        }

        if (Guess < secretNum)
        {
            cout << "That is too low.";
        }

        if (Guess > secretNum)
        {
            cout << "That is too high.";
        }

    }
    return 0;
}

【讨论】：

【解决方案5】：

您缺少两个 curly braces 以扩大您的 while 循环的范围。请注意，如果没有大括号，C++ 中任何循环的范围都将在第一个分号处停止。这是一个可行的解决方案：

#include <iostream>
#include <string>
using namespace std;

int main()
{

      string userName;

      cout << "Hello there.\n";
      cout << "My name is TARS. \n";
      cout << "What is your name? \n";
      getline(std::cin, userName);

      cout << userName << ", let's play a game.\n";

      int secretNum;
      secretNum = rand() % 20 + 1;

      cout << "I'm thinking of a number between 1-20.\n";

      int Guess;
      bool conti = true;

      while (conti) 
      {  // <-- This curly brace was missing

          cout << "Guess what it is. \n";
          cin >> Guess;

          if (Guess == secretNum)
          {
              cout << "You read my mind!";
              conti = false;
          }

          if (Guess < secretNum)
          {
              cout << "That is too low.";
          }

          if (Guess > secretNum)
          {
            cout << "That is too high.";
          }


      } // <-- This curly brace was also missing

      return 0;

}

【讨论】：