Problem - D - Codeforces

题意：

思路：

直接搜索即可，对于每个连通块都去染色，对于每一个色块都维护这个色块的墙壁数

或者麻烦点用并查集维护也行

Code：

int n, m, k;
bool st[N][N];
char g[N][N];
int ans[N * N];
int id[N][N];
 
int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};
 
void dfs(int sx, int sy, int cnt)
{
    st[sx][sy] = 1;
    id[sx][sy] = cnt;
    for(int i = 0; i < 4; i ++ )
    {
        int tx = sx + dx[i], ty = sy + dy[i];
        if(tx < 0 || tx >= n || ty >= m || ty < 0 || st[tx][ty]) continue;
        
        if(g[tx][ty] == '*') ans[cnt] ++;
        else dfs(tx, ty, cnt);
    }
}
 
 
signed main()
{
    FAST
    
    cin >> n >> m >> k;
    for(int i = 0; i < n; i ++ ) cin >> g[i];
    
    int cnt = 0;
    for(int i = 0; i < n; i ++ )
        for(int j = 0; j < m; j ++ )
            if(!st[i][j] && g[i][j] == '.') dfs(i, j, cnt ++ );
    
    
    while(k --)
    {
        int x, y; cin >> x >> y;
        x --, y --;
        
        cout << ans[id[x][y]] << '\n';
    }
    
    return 0;
}

#include <bits/stdc++.h>

#define int long long

using namespace std;

const int mxn=1e3+10;
const int mxv=1e6+10;
const int mod=1e9+7;

string s[mxn];

set<array<int,4> > S2;
multiset<pair<int,int> > S[mxv];

int N,M,K,x,y;
int F[mxv],st[mxn][mxn];
int dx[4]={-1,0,1,0},dy[4]={0,-1,0,1};

int find(int x){
	return F[x]=(x==F[x])?x:find(F[x]);
}
void join(int u,int v){
	int f1=find(u),f2=find(v);
	if(f1!=f2) F[f1]=f2;
}
bool check(int x,int y){
	return x>=1&&x<=N&&y>=1&&y<=M;
}
int calc(int x,int y){
	return (x-1)*M+y;
}
void dfs(int x,int y){
	//cout<<x<<" "<<y<<'\n';
	for(int i=0;i<4;i++){
		int vx=x+dx[i];
		int vy=y+dy[i];
		if(check(vx,vy)&&!st[vx][vy]){
			if(s[vx][vy]=='.'){
				st[vx][vy]=1;
				join(calc(x,y),calc(vx,vy));
				//cout<<calc(x,y)<<" "<<calc(vx,vy)<<'\n';
				dfs(vx,vy);
			}else{
				S2.insert({x,y,vx,vy});
				//cout<<x<<" "<<y<<" "<<vx<<" "<<vy<<'\n';
			}
		}
	}
}
void solve(){
	cin>>N>>M>>K;
	for(int i=1;i<=N;i++){
		cin>>s[i];
		s[i]=" "+s[i];
	}
	for(int i=1;i<=N;i++){
		for(int j=1;j<=M;j++) F[calc(i,j)]=calc(i,j);
	}
	for(int i=1;i<=N;i++){
		for(int j=1;j<=M;j++){
			if(!st[i][j]&&s[i][j]=='.'){
				st[i][j]=1;
				dfs(i,j);
			}
		}
	}
	for(auto v:S2){
		S[find(calc(v[0],v[1]))].insert({v[2],v[3]});
	}
	for(int i=1;i<=K;i++){
		cin>>x>>y;
		cout<<S[find(calc(x,y))].size()<<'\n';
	}
}
signed main(){
	ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	int __=1;//cin>>__;
	while(__--)solve();return 0;
}