1 /** 2  * @(#)Main.java 3  * 4  * 5  * @author  6  * @version 1.00 2014/12/21 7  */ 8 import java.util.*; 9 import java.math.*;10 11 public class Main {12     //public static BigInteger a [] = new BigInteger[10001];13     public static void main(String [] args){14         Scanner input = new Scanner(System.in);15         int n;16         while(input.hasNext()){17             n = input.nextInt();18             BigInteger a [] = new BigInteger[2];19             a[0] = new BigInteger("1");20             for(int i = 1; i<=n ; i++){21                 String s = Integer.toString(i);22                 a[i&1] = new BigInteger(s);23             //        a[i].valueOf(i);24                 a[i&1] = a[i&1].multiply(a[1-(i&1)]);25             }26         27             System.out.println(a[n&1]);28         }29     }30     31     32 }

  1 #include <cstdio>  2 #include <cstring>  3 #include <algorithm>  4 using namespace std ;  5   6 typedef long long LL ;  7   8 #define rep( i , a , b ) for ( int i = a ; i < b ; ++ i )  9 #define For( i , a , b ) for ( int i = a ; i <= b ; ++ i ) 10 #define rev( i , a , b ) for ( int i = a ; i >= b ; -- i ) 11  12 const int M = 10000 ; 13  14 struct BigInt { 15     int digit[10000] ; 16     int length ; 17  18     BigInt () { 19         length = 0 ; 20         memset ( digit , 0 , sizeof digit ) ; 21     } 22  23     BigInt ( LL number ) { 24         length = 0 ; 25         memset ( digit , 0 , sizeof digit ) ; 26         while ( number ) { 27             digit[length ++] = number % M ; 28             number /= M ; 29         } 30     } 31  32     int operator [] ( const int index ) const { 33         return digit[index] ; 34     } 35  36     int& operator [] ( const int index ) { 37         return digit[index] ; 38     } 39  40     BigInt fix () { 41         while ( length && digit[length - 1] == 0 ) -- length ; 42         return *this ; 43     } 44  45     BigInt operator + ( const BigInt& a ) const { 46         BigInt c ; 47         c.length = max ( length , a.length ) + 1 ; 48         int add = 0 ; 49         rep ( i , 0 , c.length ) { 50             add += a[i] + digit[i] ; 51             c[i] = add % M ; 52             add /= M ; 53         } 54         return c.fix () ; 55     } 56  57     BigInt operator - ( const BigInt& a ) const { 58         BigInt c ; 59         c.length = max ( a.length , length ) ; 60         int del = 0 ; 61         rep ( i , 0 , c.length ) { 62             del += digit[i] - a[i] ; 63             c[i] = del ; 64             del = 0 ; 65             if ( c[i] < 0 ) { 66                 int tmp = ( c[i] - 1 ) / M + 1 ; 67                 c[i] += tmp * M ; 68                 del -= tmp ; 69             } 70         } 71         return c.fix () ; 72     } 73  74     BigInt operator * ( const BigInt& a ) const { 75         BigInt c ; 76         c.length = a.length + length ; 77         rep ( i , 0 , length ) { 78             int mul = 0 ; 79             For ( j , 0 , a.length ) { 80                 mul += digit[i] * a[j] + c[i + j] ; 81                 c[i + j] = mul % M ; 82                 mul /= M ; 83             } 84         } 85         return c.fix () ; 86     } 87  88     void show () { 89         printf ( "%d" , digit[length - 1] ) ; 90         rev ( i , length - 2 , 0 ) printf ( "%04d" , digit[i] ) ; 91         printf ( "\n" ) ; 92     } 93  94 } ; 95  96  97 int main () 98 { 99     int n;100     while (~scanf("%d" , &n)) {101         BigInt big[2];102         big[0] = BigInt(1);103         for(int i = 1 ; i<=n ; i++)104             big[i&1] = big[1-(i&1)] * BigInt(i);105         big[n&1].show();106     }107     return 0 ;108 }