【 Leetcode string, the string transform/hexadecimal conversion 】 HJ1. The length of the string last word HJ2. Calculation of a certain number of characters appear HJ30. String merging processing

HJ1.字符串最后一个单词的长度

1.问题描述

2.解决方案

简单的JavaJust enter a string

import java.io.InputStream;
import java.util.*;

public class Main{
    
    public static void main(String [] args) throws Exception{
    
        List<String> list = new ArrayList<>();
        Scanner in = new Scanner(System.in);
        while(in.hasNext()){
    
            String str = in.next();
            list.add(str);
        }
        System.out.println(list.get(list.size()-1).length());
    }
}

HJ2.计算某字符出现次数

1.问题描述

2.解决方案

Directly delete the characters given later,Then compare the length before and after deletion to know,出现次数了！
使用API：str1.replaceAll(str2, “”)

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

public class Main {
    
    public static void main(String[] args) throws IOException {
    
        Scanner in = new Scanner(System.in);
        String str1 = in.nextLine().toUpperCase();
        String str2 = in.next().toUpperCase();
        String str3 = str1.replaceAll(str2, "");
        System.out.println(str1.length()-str3.length());
    }
}

HJ30.字符串合并处理

1.问题描述

2.解决方案

Just convert it according to the title,But there are a lot of base conversion relatedAPI的使用,可以回来reviewon a regular basis

import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.*;

public class Main{
    
    public static void main(String[] args) throws Exception{
    
        //Enter and splice
        Scanner in = new Scanner(System.in);
        String str = in.next() + in.next();
        //Parity is sorted and returned
        List<Character> list1 = new ArrayList<>();
        List<Character> list2 = new ArrayList<>();
        for(int i=0;i<str.length();i++){
    
            if(i%2==0) list1.add(str.charAt(i));
            else list2.add(str.charAt(i));
        }
        Collections.sort(list1);
        Collections.sort(list2);
        StringBuilder sb = new StringBuilder();
        int p1 = 0;
        int p2 = 0;
        for(int i=0;i<str.length();i++){
    
            Character c = i%2==0 ? list1.get(p1++) : list2.get(p2++);
            sb.append(c);
        }
        //转换操作
        for(int i=0;i<sb.length();i++){
    
            //判断是否是'0'~'9'、'A'~'F'和'a'~'f'字符
            if(!( ('0'<=sb.charAt(i)&&sb.charAt(i)<='9') || ('a'<=sb.charAt(i)&&sb.charAt(i)<='f') || ('A'<=sb.charAt(i)&&sb.charAt(i)<='F'))) continue;
            //a->10
            int a = Integer.parseInt(String.valueOf(sb.charAt(i)), 16);
            //二进制串
            String str0 = Integer.toBinaryString(a);
            //Requires leading zeros
            while(str0.length()!=4){
    
                str0 = "0"+str0;
            }
            //Reverse binary string
            String str1 = (new StringBuilder(str0)).reverse().toString();
            //Binary strings to numbers Number to hexadecimal string
            int b = Integer.parseInt(str1, 2);
            String str3 = Integer.toHexString(b).toUpperCase();
            sb.replace(i,i+1,str3);
        }
        //输出
        System.out.println(sb.toString());
    }
}