牛客网——10进制 VS 2进制

链接：https://www.nowcoder.com/questionTerminal/fd972d5d5cf04dd4bb4e5f027d4fc11e
来源：牛客网

//十进制数转化为二进制数，逆序反转后转化为十进制数
import java.util.*;
import java.math.BigInteger;
public class Main {
    public static void main(String[] args) {     // write your code here
        Scanner in=new Scanner(System.in);
        while (in.hasNext()){
            String s1=in.nextLine();
            BigInteger a=new BigInteger(s1,10);//十进制的大整数
            StringBuffer sb=new StringBuffer();
            //二进制数只有转化成字符串才能反转
            String s2=sb.append(a.toString(2)).reverse().toString();
            BigInteger b=new BigInteger(s2,2);
            System.out.println(b.toString(10));
        }
    }
}