蓝桥杯 矩阵翻硬币

思路：

参考了http://blog.csdn.net/snailset/article/details/26752435，思路很清晰。

用java实现了高效的牛顿迭代法。

我tm都要爱上java了。

实现：

import java.math.*;
import java.util.*;

public class Main {

    public static BigInteger sqrt(BigInteger x){
        if (x .equals(BigInteger.ZERO) || x.equals(BigInteger.ONE)) {
            return x;
        }
        BigInteger two = BigInteger.valueOf(2L);
        BigInteger y;
        for (y = x.divide(two);
             y.compareTo(x.divide(y)) > 0;
             y = ((x.divide(y)).add(y)).divide(two));
        return y;
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        BigInteger n;
        Scanner s = new Scanner(System.in);
        BigInteger a = s.nextBigInteger();
        BigInteger b = s.nextBigInteger();
        BigInteger ia = sqrt(a);
        BigInteger ib = sqrt(b);
        System.out.println(ia.multiply(ib));
    }
}