论状压记忆化搜索

其实非常简单，甚至比递推写法简单
比如P2704，递推做这个比较麻烦，但状压记搜强大

#include<bits/stdc++.h>
#include<bits/extc++.h>
using namespace std;
using namespace __gnu_cxx;
using namespace __gnu_pbds;
int n,m,k[101];
char x;
bitset<10> bs;
int mem[1<<11][1<<11][101];
int dfs(unsigned f,unsigned ff,int l){
	if(l==n)return 0;
	if(mem[f][ff][l])return mem[f][ff][l];
	int ans=0;
	unsigned ym=k[l]&~f&~ff;
	for(unsigned i=ym;;i=(i-1)&ym){
		if(i&(i<<1))continue;
		if(i&(i<<2))continue;
		if(i&(i>>1))continue;
		if(i&(i>>2))continue;
		ans=max(ans,dfs(i,f,l+1)+__builtin_popcount(i));
		if(!i)break;
	}
	return mem[f][ff][l]=ans;
}
int main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	cin >> n >> m;
	for(int i=0;i<n;i++){
		for(int j=0;j<m;j++)cin >> x,bs[j]=x=='P'?1:0;
		k[i]=bs.to_ulong();
	}
	cout << dfs(0,0,0);
	return 0;
}