BZOJ1211: [HNOI2004]树的计数

 1 #include<cstdio>
 2 
 3 #include<cstdlib>
 4 
 5 #include<cmath>
 6 
 7 #include<cstring>
 8 
 9 #include<algorithm>
10 
11 #include<iostream>
12 
13 #include<vector>
14 
15 #include<map>
16 
17 #include<set>
18 
19 #include<queue>
20 
21 #include<string>
22 
23 #define inf 1000000000
24 
25 #define maxn 50000
26 
27 #define maxm 500+100
28 
29 #define eps 1e-10
30 
31 #define ll long long
32 
33 #define pa pair<int,int>
34 
35 #define for0(i,n) for(int i=0;i<=(n);i++)
36 
37 #define for1(i,n) for(int i=1;i<=(n);i++)
38 
39 #define for2(i,x,y) for(int i=(x);i<=(y);i++)
40 
41 #define for3(i,x,y) for(int i=(x);i>=(y);i--)
42 
43 #define mod 1000000007
44 
45 using namespace std;
46 
47 inline int read()
48 
49 {
50 
51     int x=0,f=1;char ch=getchar();
52 
53     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
54 
55     while(ch>=‘0‘&&ch<=‘9‘){x=10*x+ch-‘0‘;ch=getchar();}
56 
57     return x*f;
58 
59 }
60 int a[maxn],n,tot;
61 bool v[maxn];
62 
63 int main()
64 
65 {
66 
67     freopen("input.txt","r",stdin);
68 
69     freopen("output.txt","w",stdout);
70 
71     n=read();
72     int sum=0;
73     for1(i,n)
74      {
75          int x=read()-1;sum+=x;
76          if(x<0||x>=n){printf("0");return 0;};
77          for1(j,x)a[++tot]=j;
78      }
79      if(n==1&&sum==-1){printf("1");return 0;}
80      if(n==1&&sum==0){printf("0");return 0;}
81     if(sum!=n-2){printf("0");return 0;}
82     sort(a+1,a+tot+1);
83     ll ans=1;
84     for1(i,n-2)
85     {
86       ans*=i;
87       for1(j,tot)
88         if(!v[j]&&ans%a[j]==0)ans/=a[j],v[j]=1;
89     } 
90     printf("%lld\n",ans);
91 
92     return 0;
93 
94 }

 1 #include<iostream>
 2 #include<cstdio>
 3 using namespace std;
 4 int n,m,c[200],i,j,sum;
 5 long long ans;
 6  
 7 int main()
 8 {
 9     freopen("input.txt","r",stdin);
10 
11     freopen("output2.txt","w",stdout);
12     cin>>n;
13     if(n==1) {cin>>m; if(m) cout<<0<<endl; else cout<<1<<endl; return 0;}
14     for(i=1;i<=n;i++)
15     {
16         scanf("%d",&m);
17         if(m<1||m>n) {cout<<0<<endl; return 0;}
18         sum+=m-1;
19         for(j=2;j<m;j++) c[j]++;
20     }
21     m=n-2;
22     if(sum!=m) {cout<<0<<endl; return 0;}
23     ans=1;
24     for(i=2;i<=m;i++)
25     {
26         ans*=i;
27         for(j=2;j<n;j++)
28             while(c[j]&&ans%j==0) c[j]--,ans/=j;
29     }
30     cout<<ans<<endl;
31     return 0;
32 }