悬关，调试2days未果，WAon2

#include <bits/stdc++.h>
using namespace std;
#define FOR(x,a,b) for(int x=a,I=b;x<=I;x++)
const int N=1e6+5;
const int dx[4]={-1,0,0,1},dy[4]={0,-1,1,0};
string s[N];
int u[N],d[N],l[N],r[N],cnt[N];
int n,m,T,sz;
void solve(){
    cin>>n>>m;
    sz=0;
    FOR(i,1,n) cin>>s[i],s[i]=" "+s[i];
    vector<vector<int>> g(n+2,vector<int>(m+2,0));
    vector<vector<int>> p(n+2,vector<int>(m+2,0));
    vector<vector<int>> vs(n+2,vector<int>(m+2,0));
    vector<int> sr(n+2,0);
    vector<int> sc(m+2,0);
    FOR(i,1,n) FOR(j,1,m){
    	if(s[i][j]=='.'){
    		sr[i]++,sc[j]++;
			continue;
		}
    	if(vs[i][j]) continue;
        queue<pair<int,int>> q;
        sz++,cnt[sz]=0;
        q.emplace(i,j),vs[i][j]=1;
        u[sz]=l[sz]=max(n,m)+1;
        d[sz]=r[sz]=0;
        while(q.size()){
			int x=q.front().first;
			int y=q.front().second;
            q.pop();
            g[x][y]=sz,cnt[sz]++;
            u[sz]=min(u[sz],x);
            d[sz]=max(d[sz],x);
            l[sz]=min(l[sz],y);
            r[sz]=max(r[sz],y);
            FOR(k,0,3){
                int tx=x+dx[k],ty=y+dy[k];
                if (1<=tx&&tx<=n&&1<=ty&&ty<=m&&vs[tx][ty]==0&&s[tx][ty]=='#'){
                    q.emplace(tx,ty);
                    vs[tx][ty]=1;
                }
            }
        }
        auto add=[&](int u,int d,int l,int r,int x){
	        p[u][l]+=x;
		    p[d+1][l]-=x;
		    p[u][r+1]-=x;
		    p[d+1][r+1]+=x;
    	};
        u[sz]=max(1,u[sz]-1);
        d[sz]=min(n,d[sz]+1);
        l[sz]=max(1,l[sz]-1);
        r[sz]=min(m,r[sz]+1);
        add(1,u[sz]-1,l[sz],r[sz],cnt[sz]);
        add(u[sz],d[sz],1,m,cnt[sz]);
        add(d[sz]+1,n,l[sz],r[sz],cnt[sz]);
    }
    int ans=0;
    FOR(i,1,n) FOR(j,1,m){
        p[i][j]+=p[i][j-1]+p[i-1][j]-p[i-1][j-1];
        ans=max(ans,p[i][j]+sr[i]+sc[j]-(s[i][j]=='.'));
    }
    cout<<ans<<endl;
}
int main(){
    cin>>T;
    while(T--) solve();
    return 0;
}