Submission

Score: 100

User: vachirasawin

Problemset: เกาะที่ใหญ่ที่สุด

Language: cpp

Time: 0.003 second

Submitted On: 2026-03-13 18:03:19

// grader-chan
// c2_st66_largest_island.cpp | c2_st66_largest_island

#include <bits/stdc++.h>
using namespace std;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    int N, M;
    cin >> N >> M;

    vector<vector<char>> world(N, vector<char>(M));
    vector<vector<bool>> visited(N, vector<bool>(M, false));
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < M; j++) {
            // Sea 0
            // Land 1
            cin >> world[i][j];
        }
    }

    int dx[4] = {+1, 0, -1, 0};
    int dy[4] = {0, +1, 0, -1};
    int ans = 0;
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < M; j++) {
            if (!visited[i][j] && world[i][j] == '1') {
                visited[i][j] = true;
                queue<pair<int, int>> q;
                q.push({i, j});
                int cnt = 1;

                while (!q.empty()) {
                    auto [x, y] = q.front();
                    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) continue;
                        if (visited[nx][ny] || world[nx][ny] == '0') continue;

                        visited[nx][ny] = true;
                        q.push({nx, ny});
                        cnt++;
                    }
                }

                ans = max(ans, cnt);
            }
        }
    }

    cout << ans;

    return 0;
}