java高精度类尝试

java高精度尝试，

poj2109，比较坑的题目

import java.io.*;  
import java.util.*;  
import java.math.*;  
public class Main {  
      
    public static void main(String[] args) {  
        Scanner in = new Scanner(System.in); 
        
        
        BigInteger mod = BigInteger.valueOf(1);  
        
        while(in.hasNext())  
        {  
            int k = in.nextInt();
            BigInteger y = in.nextBigInteger();
            BigInteger l = BigInteger.valueOf(1);
            BigInteger r = y;
            BigInteger mid, ans;
            while(l.compareTo(r) == -1){
                mid = (l.add(r)).divide(BigInteger.valueOf(2));
                ans = BigInteger.valueOf(1);
                int temp = k;
                while(temp != 0){
                    ans = ans.multiply(mid);
                    temp = temp - 1;
                }
                if(ans.compareTo(y) == -1) l = mid.add(BigInteger.valueOf(1));
                else r = mid;
            }
            ans = BigInteger.valueOf(1);
            int temp = k;
            while(temp != 0){
                ans = ans.multiply(l);
                temp = temp - 1;
            }
            if(ans.compareTo(y) == 1) l = l.subtract(BigInteger.valueOf(1));
            System.out.println(l);
        }  
          
    }  
}