大数开根号java模板

利用逼近的思路直接二分开方找出值

package lanqiao;

import java.math.BigInteger;
import java.util.Scanner;
public class Main {

    static BigInteger cal(BigInteger x){
        BigInteger l = BigInteger.ONE ;
        BigInteger r = x ;
        BigInteger temp = BigInteger.ZERO ;
        while(!l.equals(r)){
            BigInteger mid = (l.add(r)).divide(BigInteger.valueOf(2)) ;
            if(temp.compareTo(BigInteger.ZERO)!=0&&temp.compareTo(mid)==0){
                break ;
            }else{
                temp = mid ;
            }
            if(temp.compareTo(BigInteger.ZERO)==0){
                temp = mid ;
            }
            if(mid.multiply(mid).compareTo(x)==1){
                r=mid ;
            }else{
                l=mid ;
            }
        }
        if(l.multiply(l).compareTo(x)==1){
            l=l.subtract(BigInteger.ONE) ;
        }
        return l;
        
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in = new Scanner(System.in) ;
        
        while(in.hasNextBigInteger()){
            BigInteger n = in.nextBigInteger() ;
            
            
            BigInteger x = cal(n) ;
            System.out.println(x);
            
        }
    }

}