Question

我一直试图解决这个问题： https://uchicago.kattis.com/problems/uchicago.rpn

似乎我有逻辑，但是，当我提交给Kattis时，我无法通过测试用例＃7，因为我得到了错误的答案＆＃34;。有人在这里，能够发现错误吗？我猜这是一个讨厌的角落案件。我可能会非常错误。

我在下面发布了我的java代码供参考。

非常感谢！

import java.util.Scanner;
import java.util.Stack;

class ReversePolishNotation
{
public static String answer()
{
    Scanner scanner = new Scanner(System.in);

    Stack<String> stack = new Stack<String>();

    StringBuilder answer = new StringBuilder(); 

    String s = scanner.nextLine();

    scanner.close();

    String[] splitStrings = s.split(" ");

    int len = splitStrings.length;

    for (int i = 0; i < len; i++)
    {
        String next = splitStrings[i];

        if (next.equals("true"))
        {
            stack.push(next);
            continue;
        }

        else if (next.equals("false"))
        {
            stack.push(next);
            continue;
        }

        try
        {
            int number = Integer.parseInt(next);
            stack.push(String.valueOf(number));
        }

        catch (NumberFormatException e)// next is an operator
        {
            if (!(stack.size() >= 2))
            {
                answer.append("SYNTAX ERROR");
                return answer.toString();
            }

            String val1 = stack.pop();
            String val2 = stack.pop();

            if ((val2.equals("true")) || (val2.equals("false")))
            {
                if (!((val1.equals("true")) || (val1.equals("false"))))
                {
                    answer.append("TYPE ERROR");
                    return answer.toString();
                }

                else// both values are boolean
                {
                    if (!((next.equals("and")) || (next.equals("or"))))
                    {
                        answer.append("TYPE ERROR");
                        return answer.toString();
                    }

                    boolean bool1 = Boolean.parseBoolean(val1);
                    boolean bool2 = Boolean.parseBoolean(val2);

                    String result = booleanHelper(bool1, bool2, next);
                    stack.push(result);
                }
            }

            else if ((val1.equals("true")) || (val1.equals("false")))
            {
                if (!((val2.equals("true")) || (val2.equals("false"))))
                {
                    answer.append("TYPE ERROR");
                    return answer.toString();
                }

                else// both values are boolean
                {
                    if (!((next.equals("and")) || (next.equals("or"))))
                    {
                        answer.append("TYPE ERROR");
                        return answer.toString();
                    }

                    boolean bool1 = Boolean.parseBoolean(val1);
                    boolean bool2 = Boolean.parseBoolean(val2);

                    String result = booleanHelper(bool1, bool2, next);
                    stack.push(result);
                }
            }

            else
            {   
                int num1 = Integer.parseInt(val1);
                int num2 = Integer.parseInt(val2);

                if (next.equals("+"))
                {
                    String result = intHelper(num1, num2, next);
                    stack.push(result);
                }

                else if (next.equals("*"))
                {
                    String result = intHelper(num1, num2, next);
                    stack.push(result);
                }


                else if (next.equals("=="))
                {
                    String result = intHelper(num1, num2, next);
                    stack.push(result);
                }

                else
                {
                    answer.append("TYPE ERROR");
                    return answer.toString();
                }
            }
        }
    }

    if ((stack.isEmpty()) || (stack.size() > 1))
    {
        answer.append("SYNTAX ERROR");
        return answer.toString();
    }

    answer.append(stack.pop());

    return answer.toString();
}

private static String intHelper(int num1, int num2, String next)
{
    StringBuilder answer = new StringBuilder();

    if (next.equals("+"))
    {
        answer.append(num1 + num2);
    }

    else if (next.equals("*"))
    {
        answer.append(num1 * num2);
    }

    else if (next.equals("=="))
    {
        if (num1 != num2) answer.append("false");
        else
        {
            answer.append("true");
        }
    }   
    return answer.toString();
}

private static String booleanHelper(boolean bool1, boolean bool2, String next)
{
    StringBuilder answer = new StringBuilder();
    if (next.equals("and")) answer.append(bool1 && bool2);

    else if (next.equals("or")) answer.append(bool1 || bool2);

    return answer.toString();
}

public static void main(String[] args)
{
    System.out.println(answer());
}
}

Answer 1

经过进一步测试后，我认为你唯一的错误是使用Boolean.getBoolean而不是Boolean.parseBoolean解析布尔值“true”和“false”。这会导致true true and（答案：错误）等输入的错误答案。

Boolean.getBoolean将读取具有给定名称的系统属性，并尝试将其解析为布尔值，而不是实际上您的字符串“true”和“false”。

为什么我在这个反向波兰表示法挑战中得到了错误的答案

1 个答案: