如何等待有效输入

Question

我正在重新进行一场战斗，它基于硬币，正面或反面。我有用户输入“H，h，T，t”来确定战斗。我的问题是我已经实现了那些只能是有效的输入，但如果我输入“G”，例如，它显示无效输入，但仍然执行。我如何让我的程序等待这些有效输入之一？谢谢！

#include <iostream> 
#include <iomanip> 
#include <cstdlib> 
#include <ctime> 
#include <sstream> 

using namespace std; 

int main() 

{ 
    //A little information about the battle 

    cout << "\t\t\tLet the\n\n"; 
    cout << "Decision of heads or tails on the coin react history\n"; 

    cout << "\t\t/---------------------\\" << endl; 
    cout << "\t\t| RETURN TO SEVEN DAYS|\n"; 
    cout << "\t\t\\---------------------/\n\n" << endl; 

    //Main Battle 

    cout << "It is July 1, 1862, the final day\n"; 
    cout << "of the Battle of Seven Days...\n\n"; 

    cout << "In this re-enactment of the second day\n"; 
    cout << "of battle, you are George B. McClellan\n"; 
    cout << "in charge of the Unionists\n\n"; 

    cout << "We will flip a coin to determine the\n"; 
    cout << "outcome of the small battles for\n"; 
    cout << "territories within the Seven Days area\n\n"; 

    cout << "You will have to predict whether the coin\n"; 
    cout << "will come up heads or tails...\n\n"; 

    cout << "In the actual Battle at Seven Days,\n"; 
    cout << "the Northern troops turned back Lee's\n"; 
    cout << "final assaults at Malvern Hill(July\n"; 
    cout << "1)....\n\n"; 

    cout << "The confederates lost about 16,000\n"; 
    cout << "men...\n\n"; 

    cout << "The Unionists lost about 20,000 men...\n\n"; 

    cout << "McClellan's failure to capture\n"; 
    cout << "Richmond, and the subsequent\n"; 
    cout << "withdrawal of the Union's Army from\n"; 
    cout << "the Yorktown Peninsula, signified the\n"; 
    cout << "end of the Peninsular Campaign\n\n"; 

    //Running through the battles 

    int battleName = 1; 

    for (; battleName <= 9; battleName += 1){ 

     cout << "Battle \t\n" << battleName << " - "; 

     switch (battleName) 
     { 
     case 1: cout << "Oak Grove "; 
      break; 
     case 2: cout << "Mechanicsville "; 
      break; 
     case 3: cout << "Gaines Mill "; 
      break; 
     case 4: cout << "Garnett Farm "; 
      break; 
     case 5: cout << "Golding Farm "; 
      break; 
     case 6: cout << "The Peach Orchard "; 
      break; 
     case 7: cout << "Savage Station "; 
      break; 
     case 8: cout << "Frayser Farm "; 
      break; 
     case 9: cout << "Malvern Hill "; 
      break; 
     } 

     //Asking the user for input 

     cout << "\nNow Now, General McClellan\n"; 
     cout << "What do you predict the coin outcome will be, \n"; 
     cout << "Heads (H) or Tails (T)? \n"; 
     cout << "Please choose either Heads or Tails:\n"; 

     string userInput; 

     cin >> userInput; 

     if (userInput == "H" || userInput == "h") 
      cout << "\n You have chosen heads!" << endl; 

     if (userInput == "T" || userInput == "t") 
      cout << "\n You have chosen tails!" << endl; 

     else if (!(userInput == "H" || userInput == "h" || userInput == "T" || userInput == "t")) 
      userInput = 'H'; 
      cout << "Invalid input. You must choose either heads or tails!\n"; 

     cout << "\t\tPlease get ready to fight, General McClellan!!\n\n\n"; 


     //random number function 

    unsigned seed = time(0); 
    srand (seed); 

    //to integers, heads or tails 

    const int MIN_VALUE = 0; 
    const int MAX_VALUE = 1; 
    int coin = 0; 

     coin = (rand() % (MAX_VALUE - MIN_VALUE +1)) + MIN_VALUE; 

    //Deciding the actual coin flip 

    cout << "The result of the coin flip was "; 

     if (coin == 0) 
      cout << "heads!\n\n\n"; 

     if (coin == 1) 
      cout << "tails!\n\n\n"; 


    //incrementing values of the winner 

    int computerScore = 0; 
    int score = 0; 



    if(((userInput == "T" || userInput == "t") && coin == 1)) 
    { 
     cout << "Well done, General \nMcClellan...\n You have defeated Lee!\n"; 
     score += 1; 
    } 

    else if(((userInput == "H" || userInput == "h") && coin == 0)) 
    { 
     cout << "Well done, General \nMcClellan...\n You have defeated Lee!\n"; 
     score += 1; 
    } 

    else 
    { 
     cout << "I am sorry, General\nMcClellan...\n But the battle goes to Lee!"; 
      computerScore += 1; 

    } 

     cout << "\n So far: McClellan " << score << " victories,\n" << "Lee " << computerScore << "\n\n\n"; 



    //Scoring 

    if (score > computerScore) 
      cout << "The results show that\n George B. McClellan\nwon the majority of the battles\nand is thus declared the victor\non July 1 1862.\n\n\n"; 

    if (score < computerScore) 
     cout << "The results show that\nRobert E Lee\nwon the majority of the battles\nand is thus declared the victor\non July 1 1862\n\n\n"; 

    } 

    return 0; 
} 

Answer 1

这里是最简单的方法，我会使用char作为输入。 编辑：char在这种情况下不起作用，它是我在C++编码时忘记的那些东西之一。

string userINput; 
while ((cin >> userInput) != "H" && userInput != "h" && 
      userInput != "T" && userInput != "t"); 

然后我就会改掉这个代码：

else if (!(userInput == "H" || userInput == "h" || userInput == "T" || userInput == "t")) 
      userInput = 'H'; 
      cout << "Invalid input. You must choose either heads or tails!\n"; 

一起。

你在这里也有一个问题，你希望别人后执行userInput = H和打印邮件，但没有{}所以它应该是这样为了工作：

else if (!(userInput == "H" || userInput == "h" || userInput == "T" || userInput == "t")) { 
      userInput = 'H'; 
      cout << "Invalid input. You must choose either heads or tails!\n"; 
    }