1088: [SCOI2005]扫雷Mine

 1 //BZOJ 1088
 2 //by Cydiater
 3 //2016.8.26
 4 #include <iostream>
 5 #include <cstring>
 6 #include <string>
 7 #include <algorithm>
 8 #include <cmath>
 9 #include <ctime>
10 #include <cstdlib>
11 #include <queue>
12 #include <map>
13 #include <iomanip>
14 #include <cstdio>
15 using namespace std;
16 #define ll long long
17 #define up(i,j,n)       for(ll i=j;i<=n;i++)
18 #define down(i,j,n)     for(ll i=j;i>=n;i--)
19 const int MAXN=1e5+5;
20 const int oo=0x3f3f3f3f;
21 inline ll read(){
22       char ch=getchar();ll x=0,f=1;
23       while(ch>‘9‘||ch<‘0‘){if(ch==‘-‘)f=-1;ch=getchar();}
24       while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}
25       return x*f;
26 }
27 ll N,a[MAXN],f[MAXN][1<<3],ans=0;
28 namespace solution{
29       inline ll col(ll num){
30             int cnt=0;
31             if(num&(1<<1))cnt++;
32             if(num&(1<<2))cnt++;
33             return cnt;
34       }
35       void init(){
36             N=read();
37             up(i,1,N)a[i]=read();
38       }
39       void dp(){
40             memset(f,0,sizeof(f));
41             f[0][0]=1;f[0][4]=1;
42             up(i,1,N)up(S,0,(1<<3)-1)if(f[i-1][S]>0){
43                   int tmp=col(S);
44                   if(a[i]-tmp==0)f[i][S>>1]+=f[i-1][S];
45                   if(a[i]-tmp==1&&i<N)f[i][(S>>1)|(1<<2)]+=f[i-1][S];
46             }
47       }
48       void output(){
49             up(i,0,(1<<3)-1)ans+=f[N][i];
50             cout<<ans<<endl;
51       }
52 }
53 int main(){
54       //freopen("input.in","r",stdin);
55       using namespace solution;
56       init();
57       dp();
58       output();
59       return 0;
60 }