BJFU 1005——Factorial of large numbers

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描述

Factorial, as we all know, is the product of all the positive integers from one up to and including a given integer. For example, factorial zero is assigned the value of one; factorial four is 1 × 2 × 3 × 4. Symbol: N! The N is the given integer. But it is hard to calculate the factorial when the N is large. Ben wrote a program to calculate N!(N<10000) when he was in grade one. So try it!

输入

The input consists of multiple test cases. One N (0<=N<=10000,integer) in a line for each test case. Process to the end of file.

输出

For each test case, print the value of N! in a single line.

样例输入

5
10
20
100

样例输出

120
3628800
2432902008176640000
93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000

这道题的大意是输入一个数，输出它的阶乘。

看到这个栗子，明显是大数高精度运算，嘿嘿，还好在刘汝佳的书上看见过。

把书中算法改造一下后交了一次TLE，T_T,被坑了一回。

之后还是看了一位大神的代码，恍然大悟，原来一个数组其实可以存一个比较大的数，而不是存0-9一位数，这样效率就大大提高了。

之后不断尝试一个数组存的位数为多少为最佳，奇怪的是当数组开到某一位时就WA了，至今还没搞明白。。。。

等下回实力高点再回头填坑算了。Orz.........

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