[SCOI2005]扫雷

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<cmath>
 4 #include<algorithm>
 5 #include<cstring>
 6 #include<cstdlib>
 7 #include<cctype>
 8 #include<vector>
 9 #include<stack>
10 #include<queue>
11 using namespace std;
12 #define enter printf("\n")
13 #define space printf(" ")
14 #define Mem(a) memset(a, 0, sizeof(a))
15 typedef long long ll;
16 typedef double db;
17 const int INF = 0x3f3f3f3f;
18 const int eps = 1e-8;
19 const int maxn = 1e4 + 5;
20 inline ll read()
21 {
22     ll ans = 0;
23     char ch = getchar(), last = ‘ ‘;
24     while(!isdigit(ch)) {last = ch; ch = getchar();}
25     while(isdigit(ch)) {ans = ans * 10 + ch - ‘0‘; ch = getchar();}
26     if(last == ‘-‘) ans = -ans;
27     return ans;
28 }
29 inline void write(ll x)
30 {
31     if(x < 0) x = -x, putchar(‘-‘);
32     if(x >= 10) write(x / 10);
33     putchar(x % 10 + ‘0‘);
34 }
35 
36 
37 int n, a[maxn];
38 
39 bool b[maxn];
40 bool judge()
41 {
42     for(int i = 1; i < n; ++i)        //判断有点多…… 
43     {
44         if(!a[i])
45         {
46             if(b[i - 1] || b[i]) return 0;
47         }
48         else if(a[i] == 1)
49         {
50             if(b[i - 1] + b[i] > 1) return 0;
51             if(b[i - 1] + b[i] == 0) b[i + 1] = 1;
52         }
53         else if(a[i] == 2) 
54         {
55             if(b[i - 1] + b[i] > 2) return 0;
56             if(b[i - 1] + b[i] < 1) return 0;
57             if(b[i - 1] + b[i] == 1) b[i + 1] = 1;
58         }
59         else
60         {
61             if(b[i - 1] + b[i] < 2) return 0;
62             if(b[i - 1] + b[i] == 2 && i < n) b[i + 1] = 1;
63         }
64     }
65     if(b[n - 1] + b[n] < a[n]) return 0;    //最后一个格子要特判，因为到头了 
66     return 1;
67 }
68 
69 int ans = 0;
70 
71 int main()
72 {
73     n = read();
74     for(int i = 1; i <= n; ++i) a[i] = read();
75     Mem(b); b[1] = 1;
76     if(judge()) ans++;
77     Mem(b); b[1] = 0;
78     if(judge()) ans++;
79     write(ans); enter;
80     return 0;
81 }