POJ 1185 炮兵阵地（状压DP入门)

http://poj.org/problem?id=1185

状压DP:

 1 #include<iostream>
 2 #include<cstring>
 3 #include<algorithm>
 4 using namespace std;
 5
 6 int dp[105][100][100];
 7 int ma[105],st[105];
 8
 9 int ok(int x)
10 {
11     return (x&(x<<1))+(x&(x<<2));
12 }
13
14 int num(int x)
15 {
16     int  sum=0;
17     while (x)
18     {
19         if (x&1) sum++;
20         x>>=1;
21     }
22     return sum;
23 }
24 int main()
25 {
26     int n,m,i,j,k,l;
27     char c;
28     cin>>n>>m;
29     memset(dp,0,sizeof(dp));
30     memset(ma,0,sizeof(ma));
31     for (i=1;i<=n;i++)
32     {
33         for (j=1;j<=m;j++)
34         {
35             cin>>c;
36             if (c==‘H‘) ma[i]+=1<<(j-1);
37         }
38     }
39     int cut=0;
40     for (i=0;i<(1<<m);i++)
41     {
42         if (!ok(i)) st[cut++]=i;
43     }
44     for (i=0;i<cut;i++)
45     {
46         if (!(ma[1]&st[i])) dp[1][i][0]=num(st[i]);
47     }
48     for (i=2;i<=n;i++)
49     {
50         for (j=0;j<cut;j++)
51         {
52             if (ma[i]&st[j]) continue;
53             for (k=0;k<cut;k++)
54             {
55                 if (ma[i-1]&st[k]) continue;
56                 if (st[k]&st[j]) continue;
57                 for (l=0;l<cut;l++)
58                 {
59                     if (ma[i-2]&st[l]) continue;
60                     if (st[l]&st[j]) continue;
61                     if (st[k]&st[l]) continue;
62                     dp[i][j][k]=max(dp[i][j][k],dp[i-1][k][l]+num(st[j]));
63                 }
64             }
65         }
66     }
67     int ans=0;
68     for (i=0;i<cut;i++)
69     {
70         for (j=0;j<cut;j++) ans=max(ans,dp[n][i][j]);
71     }
72     cout<<ans<<endl;
73 }