HDOJ 1133 Buy the Ticket

题意：有m个带50元的人和n个带100元的人，开始时收银台没有钱，每张票卖50，并且结束时没有50元，求有多少种排队的顺序

链接：http://acm.hdu.edu.cn/showproblem.php?pid=1133

思路：可以求出公式ans=(m+n)!*(m-n+1)/(m+1)

注意点：唔

以下为AC代码：

Run ID	Submit Time	Judge Status	Pro.ID	Exe.Time	Exe.Memory	Code Len.	Language	Author
12742559	2015-01-20 10:09:55	Accepted	1133	312MS	9744K	823 B	Java	luminous11

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

public class Main{
public static void main(String args[]){
Scanner cin = new Scanner(System.in);
int ncase = 0;
while ( cin.hasNext() ){
ncase ++;
BigInteger a = new BigInteger("1");
int c = cin.nextInt();
int b = cin.nextInt();
if ( c == 0 && b == 0 ){
break;
}
System.out.printf("Test #%d:%n", ncase);
if ( c < b ){
System.out.println("0");
continue;
}
for ( int i = 1; i <= c+b; i ++ ){
BigInteger tmp = new BigInteger(((Integer)i).toString());
a = a.multiply(tmp);
}
BigInteger tmp = new BigInteger(((Integer)(c-b+1)).toString());
a = a.multiply(tmp);
tmp = new BigInteger(((Integer)(c+1)).toString());
a = a.divide(tmp);
System.out.println(a);
}
}
}