딩코딩 : Computer Science 블로그

https://www.acmicpc.net/problem/16946

#include <bits/stdc++.h>

using namespace std;

int n, m;

int arr[1001][1001];
vector<pair<int, int> > wall;
bool ch[1001][1001];
int dx[4] = { 1,0,-1,0 };
int dy[4] = { 0,1,0,-1 };

int num[1001][1001];
int marked[1001*1001]; // cnt[mark] = 개수 


int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
   
    cin >> n >> m;
    for (int i = 0; i < n; i++) {

        string s;
        cin >> s;
        for (int j = 0; j < m; j++) {
            arr[i][j] = s[j]-'0';
            if (arr[i][j]) wall.push_back({ i,j });
        }
    }

    int mark = 1;
	queue<pair<int, int> > Q;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            
            if (arr[i][j] == 0 && num[i][j] == 0) {
				int cnt = 1;
                Q.push({ i,j });
                num[i][j] = mark;
                while (!Q.empty()) {
                    int x = Q.front().first;
                    int y = Q.front().second;
                    Q.pop();

                    for (int k = 0; k < 4; k++) {
                        int nx = x + dx[k];
                        int ny = y + dy[k];

                        if (nx < 0 || nx >= n || ny < 0 || ny >= m || num[nx][ny] || arr[nx][ny]) continue;
                        Q.push({ nx,ny });
                        cnt++;
                        num[nx][ny] = mark;
                    }
                }
				marked[mark] = cnt;
				mark++;
            }
        }
    }

    for (int i = 0; i < wall.size(); i++) {
        int x = wall[i].first;
        int y = wall[i].second;

        int wall_cnt = 1;
        set<int> s;

        for (int j = 0; j < 4; j++) {
            int nx = x + dx[j];
            int ny = y + dy[j];

			if (nx < 0 || nx >= n || ny < 0 || ny >= m || arr[nx][ny] > 0) continue;
            s.insert(num[nx][ny]);
        }

        for (auto k : s) {
            wall_cnt += marked[k];
        }
        arr[x][y] = (wall_cnt % 10);
    }




    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            cout << arr[i][j];
        }
        cout << '\n';
    }
    return 0;
}