Blue Bridge Cup Test Questions Algorithm Training Binary Numbers (JAVA)

Problem description
　　Given L, R. Count the sum of the number of "1"s contained in the binary system of all the numbers in the [L,R] interval.
　　For example, the binary value of 5 is 101, which contains 2 "1"s.
　　
Input format 　　The
　　first line contains two numbers L,R.
Output format
　　A number S, which represents the sum of the number of "1" contained in the binary system of all the numbers in the [L,R] interval.
　　
Sample input
  2 3
Sample output
  3

Data scale and agreement
　　L<=R<=100000;

Problem solution:
  first convert all the numbers in the [L,R] interval into binary numbers in turn, and then obtain the characters of the binary numbers one by one, and judge whether it is '1', if it is temp++;

code show as below:

import java.util.ArrayList;
import java.util.Scanner;

public class BinaryOne {
    
    
	public static void main(String[] args) {
    
    
		int temp=0;
		Scanner scanner=new Scanner(System.in);
		int L=scanner.nextInt();
		int R=scanner.nextInt();
		for(int i=L;i<=R;i++) {
    
    
			String string=two(i);//10000
			
			for(int j=0;j<string.length();j++) {
    
    
				char a=string.charAt(j);
				if(a=='1') {
    
    
					temp++;
				}
			}	
		}
		System.out.println(temp);	
	}
	
	public static String two(int a) {
    
    
		ArrayList<String> list=new ArrayList();
		while(a!=0) {
    
    		
			list.add(a%2+"");
			 a=a/2;	
		}
		String two="";
		for(int i=list.size()-1;i>=0;i--) {
    
    
			two+=list.get(i);
		}		
		return two;
	}
}