rt，感谢各位大佬

#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
int h[110], p[110], b[110], cnt;
int f[110][110][110];
int main()
{
	int n, m;
	scanf("%d%d", &n, &m);
	for (int i = 0; i < (1 << m); i++)
	{
		if ((i & (i << 1)) || (i & (i << 2))) continue;
		p[++cnt] = i;
		int t = i;
		while (t)
		{
			b[cnt] += t & 1;
			t >>= 1;
		}
	}
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= m; j++)
		{
			char c;
			scanf(" %c", &c);
			h[i] <<= 1;
			h[i] += (c == 'H');
		}
	for (int j = 1; j <= cnt; j++)
	{
		if (p[j] & h[1]) continue;
		else f[1][j][1] = b[j];
	}
	for (int i = 2; i <= n; i++)
		for (int j = 1; j <= cnt; j++)
		{
			if (p[j] & h[i]) continue;
			for (int k = 1; k <= n; k++)
			{
				if (p[k] & h[i - 1]) continue;
				if (p[k] & p[j]) continue;
				for (int l = 1; l <= n; l++)
				{
					if (p[l] & h[i - 2]) continue;
					if (p[l] & p[k]) continue;
					if (p[l] & p[j]) continue;
					f[i][j][k] = max(f[i][j][k], f[i - 1][k][l] + b[j]);
				}
			}
		}
	int ans = 0;
	for (int j = 1; j <= cnt; j++)
		for (int k = 1; k <= cnt; k++) 
			ans = max(ans, f[n][j][k]);
	printf("%d\n", ans);
	return 0;
}