ACM 2008 杭州的C题

试试看java的BigInteger的

java写出来好丑哇

直接枚举k,不用判p, q的素数

import java.io.*;
import java.util.*;
import java.math.*;
public class Main
{
            public static BigInteger sqrt(BigInteger a)
            {
                BigInteger l = BigInteger.ONE;
                BigInteger h = a;
                while (l.compareTo(h)<0)
                {
                    BigInteger m = l.add(h).divide(BigInteger.valueOf(2));
                    int tmp = m.pow(2).compareTo(a);
                    if (tmp == 0)
                    {
                       // System.out.println("sqrt return "+a.toString()+' '+m.toString());
                        return m;
                    }
                    if (tmp < 0) l = m.add(BigInteger.ONE);
                    else
                        h = m.subtract(BigInteger.ONE);
                }
                return l;
            }
            public static void main(String args[]) throws Exception
            {
                    Scanner cin=new Scanner(new BufferedInputStream(System.in));
                    int ctr = 0;
                    while (cin.hasNextBigDecimal())
                    {
                        
                  
                        BigInteger n = cin.nextBigInteger();
                        BigInteger d = cin.nextBigInteger();
                        BigInteger e = cin.nextBigInteger();
                        if (n.compareTo(BigInteger.ZERO)==0)
                            return ;
                        //System.out.println(n.toString()+ ' '+ d.toString()+ ' '+ e.toString());
                        for (int kk = 1; kk < 100; kk++)
                        {
                            BigInteger k = BigInteger.valueOf(kk);
                         //  System.out.println("k = "+k.toString());
                            BigInteger tmp = d.multiply(e).subtract(BigInteger.ONE).mod(k);
                            if (tmp.compareTo(BigInteger.ZERO) == 0)
                            {
                                BigInteger b = d.multiply(e);
                             //   System.out.println("b = "+b.toString());
                                b = b.subtract(BigInteger.ONE);
                                b = b.divide(k);
                              //  System.out.println("b = "+b.toString());
                                b = b.subtract(n).subtract(BigInteger.ONE);
                                b = BigInteger.ZERO.subtract(b);
                               // System.out.println("b = "+b.toString());
                                if (b.compareTo(BigInteger.ZERO) >= 0)
                                {
                                    BigInteger delt = b.pow(2).subtract(n.multiply(BigInteger.valueOf(4)));
                                    
                                    BigInteger ddelt = sqrt(delt);
                                   // System.out.println("delt = "+delt.toString()+"ddelt = "+ddelt.toString());
                                    if (ddelt.pow(2).compareTo(delt) == 0)
                                    {
                                        BigInteger p = b.subtract(sqrt(delt)).divide(BigInteger.valueOf(2));
                                        BigInteger q = b.add(sqrt(delt)).divide(BigInteger.valueOf(2));

                                        if (e.gcd(p.subtract(BigInteger.ONE).multiply(q.subtract(BigInteger.ONE))).compareTo(BigInteger.ONE) == 0)
                                        {
                                            ctr += 1;
                                            System.out.print("Case #");
                                            System.out.print(ctr);
                                            System.out.println(": "+p.toString()+' '+q.toString());
                                            break;
                                        }
                                    }
                                }

                            }
                        }
                    }
                   
            }