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()) ;
             if(temp.compareTo(BigInteger.ZERO)!=&&temp.compareTo(mid)==){
                 break ;
             }else{
                 temp = mid ;
             }
             if(temp.compareTo(BigInteger.ZERO)==){
                 temp = mid ;
             }
             if(mid.multiply(mid).compareTo(x)==){
                 r=mid ;
             }else{
                 l=mid ;
             }
         }
         if(l.multiply(l).compareTo(x)==){
             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);

         }
     }

 }