SGU 111 Very simple problem

SGU_111

    又一次写大数开平方了，由于Java写起来比较方便，所以就直接用Java写了。

import java.math.BigInteger;
import java.util.Scanner;

public class Solution {
    public static void main(String[] args) {
        Scanner cin = new Scanner(System.in);
        BigInteger X;
        while(cin.hasNext())
        {
            X = cin.nextBigInteger();
            System.out.println(Sqrt(X));
        }
    }
    public static BigInteger Sqrt(BigInteger n)
    {
        int i, k;
        BigInteger div, ans, c;
        String s = "0" + n.toString();
        if(s.length() % 2 == 0)
            i = 1;
        else
            i = 2;
        ans = new BigInteger("0");
        c = new BigInteger("0");
        for(;i < s.length(); i += 2)
        {
            div = ans.multiply(BigInteger.valueOf(20));
            c = c.multiply(BigInteger.valueOf(100)).add(new BigInteger(s.substring(i - 1, i + 1)));
            for(k = 0; k < 10; k ++)
                if(div.add(BigInteger.valueOf(k + 1)).multiply(BigInteger.valueOf(k + 1)).compareTo(c) == 1)
                    break;
            ans = ans.multiply(BigInteger.valueOf(10)).add(BigInteger.valueOf(k));
            c = c.add(div.add(BigInteger.valueOf(k)).multiply(BigInteger.valueOf(k)).negate());
        }
        return ans;
    }
}