poj 1185 炮兵阵地 //状态压缩DP

注意只有一行等这些特殊情况

这种状态压缩DP还是比较简单的，这个题是前2行推出下一行的状态

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int MAXN = (1 << 10);
int n, m;
char s[12];
int state[101][100];
int dp[2][100][100];//循环数组
int num[MAXN];
void init()
{
    for(int i = 0; i < MAXN; i++)
    {
        int temp = i;
        num[i] = 0;
        while(temp)
        {
            if(temp & 1) num[i]++;
            temp >>= 1;
        }
    }
}
void get_state(int id, int val)
{
    state[id][0] = 0;
    for(int i = 0; i <= val; i++)
    {
        if((i | val) != val)  continue;
        if((i & (i << 1)) || (i & (i >> 1)))  continue;
        if((i & (i << 2)) || (i & (i >> 2)))  continue;
        state[id][++state[id][0]] = i;
    }
}
int main()
{
    init();
    while(scanf("%d%d", &n, &m) != EOF)
    {
        for(int i = 0; i < n; i++)
        {
           scanf("%s", s);
           int val = 0;
           for(int j = 0; j < m; j++)
           {
               val <<= 1;
               if(s[j] == 'P')  val += 1;
           }
           get_state(i, val);
        }

        int sum = 0;
        for(int i = 1; i <= state[0][0]; i++)
        {
            dp[0][i][0] = num[state[0][i]];
            sum = max(sum, dp[0][i][0]);
        }

        for(int i = 1; i <= state[1][0]; i++)
        {
            for(int j = 1; j <= state[0][0]; j++)
            {
                dp[1][i][j] = -1;
                if(state[1][i] & state[0][j])  continue;
                dp[1][i][j] = dp[0][j][0] + num[state[1][i]];
                sum = max(sum, dp[1][i][j]);
            }
        }

        for(int i = 2; i < n; i++)
        {
            int a = i % 2;
            int b = 1 - a;
            for(int x = 1; x <= state[i][0]; x++)
            {
                for(int y = 1; y <= state[i-1][0]; y++)
                {
                    dp[a][x][y] = -1;
                    if(state[i][x] & state[i-1][y])  continue;
                    for(int z = 1; z <= state[i-2][0]; z++)
                    {
                        if(state[i][x] & state[i-2][z])  continue;
                        if(state[i-1][y] & state[i-2][z])  continue;
                        if(dp[b][y][z] == -1)  continue;
                        dp[a][x][y] = max(dp[a][x][y], dp[b][y][z] + num[state[i][x]]);
                        //if(i == n - 1 && dp[a][x][y] > 0)  printf("%d\n",dp[a][x][y]);
                    }
                }
            }
        }

        int a = (n - 1) % 2;
        for(int i = 1; i <= state[n-1][0]; i++)
          for(int j = 1; j <= state[n-2][0]; j++)
          {
              if(dp[a][i][j] > sum) sum = dp[a][i][j];
          }

        printf("%d\n",sum);
    }
    return 0;
}