Question

我是C ++和编程的新手，我需要一些帮助。我不明白为什么当计算机猜到我的号码时它会无限循环。目前我已经把最终功能放在了一边。任何建议将不胜感激。

// Computer guesses number

#include <iostream>
#include <ctime>
#include <cstdlib>

using namespace std;

int main()
{
    srand(static_cast<unsigned int>(time(0))); // Generates random number

    int myNumber; // My number.
    int computersNumber = 0; 
    int tries = 0;
    int highest = 100; // Highest number the computer has put.
    int lowest = 1; // Lowest number the computer has put.

    cout << "\tHello, in this game the computer will try to find your number.\n\n";
    cout << "Please insert your number ( 1 - 100 ): ";
    cin >> myNumber; // My number, that the computer is going to guess.

    while (myNumber <= 0 || myNumber >= 101) // Checks if user has inputed a legal number.
    {
        cout << "You entered an illegal number. Please type a new one.\n";
        cin >> myNumber; // If user made an illegal choice it asks to input a new one.
    } 

    do
    {
        int computersNumber = rand() % (highest - lowest) + lowest;
        ++tries; // adds +1 every time computer guesses wrong number.

        if (myNumber > computersNumber)
        {
            cout << "The computer guessed: " << computersNumber << "\n";
            lowest = computersNumber + 1;
        }
        else if (myNumber < computersNumber)
        {
            cout << "The computer guessed: " << computersNumber << "\n";
            highest = computersNumber - 1;
        }
        else
        {
            cout << "Computer guessed your number in " << tries << " tries.\n";
            break; // infinite loop if this wasn't here.
        }

    } while (myNumber != computersNumber);

    return 0;
}

Answer 1

您的问题是您在do-while循环中重新声明computersNumber。这将创建一个新的本地变量实例，该实例使用do-while中的所有内容，但while()语句中的条件仍然引用computersNumber方法中声明的main()变量因为int computersNumber = rand() % (highest - lowest) + lowest;告诉C ++在do-while循环中创建一个新变量，而不是修改main内的原始变量，因此不会被更改。

要解决此问题，请更改此行：

int computersNumber = rand() % (highest - lowest) + lowest;

对此：

computersNumber = rand() % (highest - lowest) + lowest;

Answer 2

您在do循环中声明了一个新变量： int computersNumber = rand() % (highest - lowest) + lowest;

此定义位于循环范围内，在do { }块之外是不可见的。

您的while (myNumber != computersNumber);条件正在检查循环外部的int computersNumber = 0;定义，该定义始终为0.

修复方法是重用循环中的现有变量而不是创建新变量，因此从以下行中删除int：

int computersNumber = rand() % (highest - lowest) + lowest;

而是使用

computersNumber = rand() % (highest - lowest) + lowest;。

Answer 3

您已在循环中声明了另一个名为/** * Create and show a simple notification containing the received FCM message. */ private void sendNotification(String messageBody, Bitmap image, String TrueOrFalse) { Intent intent = new Intent(this, MainActivity.class); intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); intent.putExtra("AnotherActivity", TrueOrFalse); PendingIntent pendingIntent = PendingIntent.getActivity(this, 0 /* Request code */, intent, PendingIntent.FLAG_ONE_SHOT); Uri defaultSoundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION); NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this) .setLargeIcon(image)/*Notification icon image*/ .setSmallIcon(R.drawable.firebase_icon) .setContentTitle(messageBody) .setStyle(new NotificationCompat.BigPictureStyle() .bigPicture(image))/*Notification with Image*/ .setAutoCancel(true) .setSound(defaultSoundUri) .setContentIntent(pendingIntent); NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE); notificationManager.notify(0 /* ID of notification */, notificationBuilder.build()); }的变量。 while语句中使用的computersNumber是您在main函数中声明的另一个变量。

您可以通过在循环中使用相同的变量来解决此问题：

更改此行

computersNumber

并删除int computersNumber = rand() % (highest - lowest) + lowest;关键字。

int

您可以在以下链接中阅读有关变量范围的更多信息：
https://www.tutorialspoint.com/cplusplus/cpp_variable_scope.htm

Answer 4

您在两个位置声明computersNumber。因此，您将一个设置为零int computersNumber = 0;，而在另一个位置，您将一个随机数分配给int computersNumber = rand() % (highest - lowest) + lowest;。

设置为零的是您正在检查的那个，因为已设置为随机数的那个仅具有已设置的每次迭代的范围。意味着循环外部{{1} }始终为零，并且在循环内部使用随机值创建新的computersNumber。因此，只要computersNumber未设置为零，就会有无限循环。

要解决此问题，只需从myNumber移除int，使其成为int computersNumber = rand() % (highest - lowest) + lowest;，每次循环时，您都会将computersNumber = rand() % (highest - lowest) + lowest;设置为随机值，如果该随机值匹配computersNumber它会打破循环。

具有do功能的无限循环

4 个答案: