牛客 HJ5 进制转换 （Java 暴力拆解）

 

 

思路：

还是暴力拆解。

收到后验证是否是16进制数。(空，0x..，长度)

循环取后面两个位并累加，做16转10

 

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;


public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String str;
        String binary = "";//2进制字符串
        int sumNum = 0;//10进制数值
        int len = 0;//16进制字符长度
        
        if((str = br.readLine())!=null){//收到读入数值字符串
               if((str.charAt(0)!='0')||(str.charAt(1)!='x'||str.length()>10)){
                   System.out.println("error input!");
               };//十六进制
                len = str.length();
                for(int i = 0;i < len-2;i++){//将16转2


                    switch(str.charAt(len-i-1)){
                        case '0':
                            binary ="0000"+binary;
                            break;
                        case '1':
                            binary ="0001"+binary;
                            break;
                        case '2':
                            binary ="0010"+binary;
                            break;
                        case '3':
                            binary ="0011"+binary;
                            break;
                        case '4':
                            binary ="0100"+binary;
                            break;
                        case '5':
                            binary ="0101"+binary;
                            break;
                        case '6':
                            binary ="0110"+binary;
                            break;
                        case '7':
                            binary ="0111"+binary;
                            break;
                        case '8':
                            binary ="1000"+binary;
                            break;
                        case '9':
                            binary ="1001"+binary;
                            break;
                        case 'A':
                            binary ="1010"+binary;
                            break;
                        case 'B':
                            binary ="1011"+binary;
                            break;
                        case 'C':
                            binary ="1100"+binary;
                            break;
                        case 'D':
                            binary ="1101"+binary;
                            break;
                        case 'E':
                            binary ="1110"+binary;
                            break;
                        case 'F':
                            binary ="1111"+binary;
                    }
                    
                }
            int num = 4*(len-2)-1;
            for(;num >= 0;num--){//按位数累加，2转10
                switch(binary.charAt(num)){
                    case '0':
                        break;
                    case '1':
                        sumNum = sumNum + (int)Math.pow(2,binary.length()-1-num);
                        break;
                }
            }
        }
        System.out.println(sumNum);
    }
}

 

错误1：

Main.java:16: error: unclosed character literal
binary = binary + '0000'
^

java中的字符串要用“”，字符是‘’

 

错误2：

Main.java:13: error: continue outside of loop
if((str.charAt(0)=='0')&&(str.charAt(1)=='x')) continue;//十六进制
^

continue 只能在循环中 用，意思是执行到continue的时候 结束此次循环，进入下一次循环。（原结构不是在循环中使用）

改为了：

 

               if((str.charAt(0)!='0')||(str.charAt(1)!='x')){
                   System.out.println("error input!");
               };//十六进制

 

错误3：

Main.java:71: error: incompatible types: possible lossy conversion from double to int
sumNum = sumNum + Math.pow(2,7-num);
^
1 error