简单改变制作程序中的奇怪计数行为[重复]

问题描述 投票:0回答:2

这个问题在这里已有答案:

所以我正在制作这个相当直接的最佳变化程序,在大多数情况下都可以完美地运行。但由于一些奇怪的原因,它行为不一致,有时不会添加所需的最后一分钱,但其他时候会。

我尝试了不同的输出,代码总是正确的,除了有时最后一分钱;使用美国货币时。我确定原因很明显,但我只是看不到它。

   public static int[] optimal_change(double[] currency, double amount) {

        int[] count = new int[currency.length];

        for (int i = 0; i < currency.length; i++) {
            if (amount >= currency[i]) {
                amount -= currency[i];
                count[i]++;
                i--;
            }
            if (amount == 0.0000) {
                break;
            }
        }

        return count;
    }
public static void main(String[] args) {

        double[] american_currency = {100,50,20,10,5,1,0.25,0.10,0.05,0.01};
        //Japanese currency: https://www.boj.or.jp/en/note_tfjgs/note/valid/index.htm/
        double[] japanese_currency = {10000,5000,2000,1000,500,100,50,10,5,1};

        int[] american_change = optimal_change(american_currency, 78.36);
        int[] japanese_change = optimal_change(japanese_currency, 793048);

        System.out.println("Optimal change for: $78.38");
        for (int i = 0; i < american_currency.length; i++) {
            if (i <= 5) {
                System.out.println(Integer.toString(american_change[i]) + " $" + Double.toString(american_currency[i]));
            } else {
                System.out.println(Integer.toString(american_change[i]) + " " + Double.toString(american_currency[i]) + "¢");
            }
        }
        System.out.println("--------------------------");
        System.out.println("Optimal change for: ¥793040");
        for (int i = 0; i < japanese_currency.length; i++) {

            System.out.println(Integer.toString(japanese_change[i]) + " ¥" + Double.toString(japanese_currency[i]));

        }


    }

正确的结果:

输入:78.37

输出:

最佳变化:78.37美元

0 $100.0

1 $50.0

1 $20.0

0 $10.0

1 $5.0

3 $1.0

1 0.25¢

1 0.1¢

0 0.05¢

2 0.01¢


结果不正确:

输入:78.38

输出:

最佳变化:78.38美元

0 $100.0

1 $50.0

1 $20.0

0 $10.0

1 $5.0

3 $1.0

1 0.25¢

1 0.1¢

0 0.05¢

2 0.01¢

输出应该是:

最佳变化:78.38美元

0 $100.0

1 $50.0

1 $20.0

0 $10.0

1 $5.0

3 $1.0

1 0.25¢

1 0.1¢

0 0.05¢

3 0.01¢

java currency greedy
2个回答
0
投票

切换到BigDecimal似乎解决了这个问题。不知道为什么双打问题持续这么长时间。但幸运的是它有效。

import java.math.BigDecimal;

public class Greedy_Money_BigInteger {
    public static int[] optimal_change(BigDecimal[] currency, BigDecimal amount) {

        int[] count = new int[currency.length];

        for (int i = 0; i < currency.length; i++) {
            //if (amount >= currency[i]) {
            if (amount.compareTo(currency[i]) >= 0) {
                amount = amount.subtract(currency[i]);
                count[i]++;
                i--;
            }
            if (amount.compareTo(BigDecimal.valueOf(0)) <= 0) {
                break;
            }
        }

        return count;
    }


    public static void main(String[] args) {

        BigDecimal[] american_currency = {BigDecimal.valueOf(100),BigDecimal.valueOf(50),BigDecimal.valueOf(20),BigDecimal.valueOf(10),BigDecimal.valueOf(5),BigDecimal.valueOf(1),BigDecimal.valueOf(0.25),BigDecimal.valueOf(0.10),BigDecimal.valueOf(0.05),BigDecimal.valueOf(0.01)};
        //Japanese currency: https://www.boj.or.jp/en/note_tfjgs/note/valid/index.htm/
        BigDecimal[] japanese_currency = {BigDecimal.valueOf(10000),BigDecimal.valueOf(5000),BigDecimal.valueOf(2000),BigDecimal.valueOf(1000),BigDecimal.valueOf(500),BigDecimal.valueOf(100),BigDecimal.valueOf(50),BigDecimal.valueOf(10),BigDecimal.valueOf(5),BigDecimal.valueOf(1)};

        BigDecimal american_change_value = BigDecimal.valueOf(78.31);
        BigDecimal japanese_change_value = BigDecimal.valueOf(793043);

        int[] american_change = optimal_change(american_currency, american_change_value);
        int[] japanese_change = optimal_change(japanese_currency, japanese_change_value);

        System.out.println("Optimal change for: $" + american_change_value.toString());
        for (int i = 0; i < american_currency.length; i++) {
            if (american_change[i] > 0) {
                if (i <= 5) {
                    System.out.println(Integer.toString(american_change[i]) + " $" + american_currency[i].toString());
                } else {
                    System.out.println(Integer.toString(american_change[i]) + " " + american_currency[i].toString() + "¢");
                }
            }
        }
        System.out.println("--------------------------");
        System.out.println("Optimal change for: ¥" + japanese_change_value.toString());
        for (int i = 0; i < japanese_currency.length; i++) {
            if (japanese_change[i] > 0) {
                System.out.println(Integer.toString(japanese_change[i]) + " ¥" + japanese_currency[i].toString());
            }
        }


    }
}

-1
投票

正如其他人在评论中指出的那样,问题是由Java的“近似”值引起的。

在BigDecimal中更改它。

有关其他信息,请参阅此question

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