java - pat的一道题，有2个测试点一直无法通过

Question

pat的一道题

提交之后有两个测试点过不去

我的代码如下

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String s = in.next();
        double fu = 0,ou = 0,a_2 = 0;
        int i = 0;
        if(s.charAt(0)==45){
            //如果是负数
            fu = 0.5;
        }
        while(i<s.length()){
            //判断2 的个数
            if((s.charAt(i)-48)==2){
                a_2++;
            }
            i++;    
        }
        if(s.charAt(s.length()-1)%2==0){
            //如果是偶数
            ou = 1.0;
        }
        double fan2 = 0;
        if(fu==0){//正数
            fan2 = a_2/((double)(s.length()));
                    
        }else{//负数        
            fan2 = a_2/(s.length()-1)*(ou+fu);
        }
        //测试2的个数/总字符串长度的值
        System.out.println(fan2);
        System.out.printf("%.2f%%",fan2*2*100);
    }
}

请问这是哪点没有通过呢？

Answer 1

The questioner did not understand the meaning of the question clearly. Negative numbers increase by 0.5 times and must be multiplied by 1.5. Even numbers increase by 1 and must be multiplied by 2.
fan2 = a_2/(s.length()-1)*(ou+fu ); // Are you multiplying the scale factor correctly?
Also positive numbers can also be even numbers. I don’t know how you passed the other cases

Answer 2

// 这一行代码是有问题的，s.charAt()返回的是一个char值，而不是int值，这里会得到char对应的ascii值转换成int值再进行运算
if(s.charAt(s.length()-1)%2==0) {

In addition, as @zjupure said, I feel that the questioner’s understanding of the question is biased, and I also understood it according to @zjupure.

But the strange thing is that the questioner’s code also passed 66.67% of the tests...

In addition, some tests may not run because the boundary conditions and input parameter verification are not judged. For example, the input is not a number, or a value like +0, -0. The subject can also add these ( Although I think it’s fucked up to write these codes as algorithm questions, but in order to pass the test...).

Answer 3

Additional point: If the first digit is a negative sign, then you need to start from the second digit to calculate whether it is 2, and the number of digits in the number