济南NOIP冬令营 选拔(select)

 1 #define LL long long
 2 
 3 #include<iostream>
 4 #include<algorithm>
 5 #include<cstring>
 6 #include<iomanip>
 7 #include<cstdio>
 8 using namespace std;
 9 
10 const int MAXN=10000;
11 const int DLEN=9;
12 const int WIDE=1000000000;
13 
14 class BigNum
15 {
16 public:
17     BigNum(){memset(NUM,0,sizeof(NUM));LEN=1;}
18     BigNum(const BigNum &A){memcpy(NUM,A.NUM,sizeof(NUM));LEN=A.LEN;}
19     BigNum(int n){memset(NUM,0,sizeof(NUM));NUM[0]=n;LEN=1;while(NUM[LEN-1]>=WIDE){NUM[LEN]+=NUM[LEN-1]/WIDE;NUM[LEN-1]%=WIDE;LEN++;}}
20     LL NUM[MAXN],LEN;
21 };
22 
23 void Output(const BigNum T)
24 {
25     cout<<T.NUM[T.LEN-1];
26     for(int i=T.LEN-2;i>=0;i--)
27     {
28         cout.width(DLEN);
29         cout.fill(‘0‘);
30         cout<<T.NUM[i];
31     }
32 }
33 
34 BigNum Mult(BigNum A,int n)
35 {
36     BigNum C(A);
37     int i,tmp,k=0;
38     for(i=0;i<C.LEN||k;i++)
39     {
40         tmp=C.NUM[i]*n+k;
41         k=tmp/WIDE;
42         C.NUM[i]=tmp%WIDE;
43     }
44     C.LEN=i;
45     return C;
46 }
47 
48 BigNum Div(BigNum A,int n)
49 {
50     BigNum C(A);
51     int k=0;
52     for(int i=C.LEN-1;i>=0;i--)
53     {
54         k=k*WIDE+C.NUM[i];
55         C.NUM[i]=k/n;
56         k%=n;
57     }
58     while(C.NUM[C.LEN-1]==0) C.LEN--;
59     return C;
60 }
61 
62 int n;
63 int a[10001];
64 BigNum A(1);
65 
66 int main()
67 {
68     freopen("select.in","r",stdin);
69     freopen("select.out","w",stdout);
70     scanf("%d",&n);
71     for(int i=1;i<=n;i++)
72     {
73         int x;
74         scanf("%d",&x);
75         a[x]++;
76     }
77     for(int i=2;i<=n;i++)
78         A=Mult(A,i);
79     for(int i=1;i<=10000;i++)
80         if(a[i]>0)
81         {
82             for(int j=2;j<=a[i];j++)
83                 A=Div(A,j);
84         }
85     Output(A);
86     return 0;
87 }