hdu 1042(大数——阶乘)

题目大意：输入n，输出n!

解题思路：数据可能很大。用java的大数

代码如下：

package com.njupt.bigInteger;

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

public class HDU_1042 {

	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		BigInteger big ;
		while(scanner.hasNextInt()){
			int n = scanner.nextInt();
			big = factorial(n);
			System.out.println(big);
		}
	}
	
	public static BigInteger factorial(int n){
		BigInteger a = new BigInteger("1");
		BigInteger b;
		for(int i = 1 ; i <= n ; ++i){
			b = new BigInteger(String.valueOf(i));//因为BigInteger的构造函数只能接受String类型的作为参数，所以要对i进行类型转换
			a = a.multiply(b);
		}
		
		return a;
	}
}