java - 二分查找函数未到达末尾

Question

import java.util.Scanner;

public class GuessingGame {

private Scanner reader;

public GuessingGame() {
    // use only this scanner, othervise the tests do not work
    this.reader = new Scanner(System.in);
}

public void play(int lowerLimit, int upperLimit) {
    instructions(lowerLimit, upperLimit);
    boolean isAboveAverage;
    int counter = -1;

    while (counter < howManyTimesHalvable(upperLimit - lowerLimit)) {
        isAboveAverage = isGreaterThan(average(lowerLimit, upperLimit));
        if (upperLimit == lowerLimit) {
            break;
        }
        if (isAboveAverage) {
            lowerLimit = average(lowerLimit, upperLimit);
        } else {
            upperLimit = average(lowerLimit, upperLimit);
        }
        counter++;
    }

    System.out.println("your number is " + upperLimit);
}

// implement here the methods isGreaterThan and average
public boolean isGreaterThan(int number) {
    boolean isGreater = false;
    boolean isCorrectAnswerGiven = false;

    while (!isCorrectAnswerGiven) {
        System.out.println("Is your number greater than " + (number) + "? (y/n)");
        String answer = reader.nextLine();

        if (answer.equals("yes") || answer.equals("y")) {
            isGreater = true;
            isCorrectAnswerGiven = true;
        } else if (answer.equals("no") || answer.equals("n")) {
            isCorrectAnswerGiven = true;
        }
    }

    return isGreater;
}

public int average(int upperLimit, int lowerLimit) {
    return (upperLimit + lowerLimit) / 2;
}

public int average2(int firstNumber, int secondNumber) {
    double res = (firstNumber + secondNumber) / 2.0;
    Math.round(res);
    //System.out.println(res);
    return (int) res;
}

public void instructions(int lowerLimit, int upperLimit) {
    int maxQuestions = howManyTimesHalvable(upperLimit - lowerLimit);

    System.out.println("Think of a number between " + lowerLimit + "..." + upperLimit + ".");

    System.out.println("I promise you that I can guess the number you are thinking with " + maxQuestions + " questions.");
    System.out.println("");
    System.out.println("Next I'll present you a series of questions. Answer them honestly.");
    System.out.println("");
}

// a helper method:
public static int howManyTimesHalvable(int number) {
    // we create a base two logarithm  of the given value

    // Below we swap the base number to base two logarithms!
    return (int) (Math.log(number) / Math.log(2)) + 1;
 }
}

我在调试此代码时遇到问题。在这个类中，我应该实现一个简单的人工智能，它根据你对问题“你的数字是否大于”+一个数字的回答来猜测一个数字。我的问题是a.代码永远不会到达给定范围的末尾(因此，范围从 1 到 10，它永远不会猜测 1 或 10)和 b。是没有及时停止。 Java经常多次重复一个问题，但是程序应该在知道答案后立即说出答案。

我的错误显然在于游戏方法(为了完整性我包括了整个类(class))，我只是不知道在哪里。我的程序可以正常运行，因此不太可能出现拼写错误或编程错误。我的逻辑一定做错了什么，但我不知道是什么。有谁知道错误出在哪里吗？

Answer 1

你的逻辑有问题:

• 您在每次迭代中计算howManyTimesHalvable。考虑到计数器的增量，这是没有意义的。它的最后一个可能值始终为 1，该值可能远低于当前计数器。
• 您在提出问题后立即检查上限和下限是否相同，而不更新这些值。只需将其移动到循环末尾即可。
• 最后一件事是，在更新 lowerLimit 时，您需要将平均值增加 1。如果“您的数字是否大于 X”的答案为"is"，则新的 lowerLimit 不能是 X。

更正方法:

public void play(int lowerLimit, int upperLimit) {
    instructions(lowerLimit, upperLimit);
    boolean isAboveAverage;
    int counter = howManyTimesHalvable(upperLimit - lowerLimit);
    while (counter > 0) {
        isAboveAverage = isGreaterThan(average(lowerLimit, upperLimit));
        if (isAboveAverage) {
            lowerLimit = average(lowerLimit, upperLimit)+1;
        } else {
            upperLimit = average(lowerLimit, upperLimit);
        }
        if (upperLimit == lowerLimit) {
            break;
        }
        counter--;
    }
    System.out.println("your number is " + upperLimit);
}