백준 BOJ 2468 C++ 안전영역

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

int n, ans, board[105][105];
bool visited[105][105];

int di[] = {1, -1, 0, 0};
int dj[] = {0, 0, 1, -1};

void bfs(int i, int j) {
    queue<pair<int, int>> q;
    visited[i][j] = true;
    q.push({i, j});
    while (!q.empty()) {
        i = q.front().first;
        j = q.front().second;
        q.pop();
        for (int k = 0; k < 4; ++k) {
            int ni = i + di[k];
            int nj = j + dj[k];
            if (ni >= 0 && ni < n && nj >= 0 && nj < n) {
                if (!visited[ni][nj]) {
                    visited[ni][nj] = true;
                    q.push({ni, nj});
                }
            }
        }
    }
}

void solve() {
    cin >> n;
    set<int> heights;
    heights.insert(0);
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            cin >> board[i][j];
            heights.insert(board[i][j]);         
        }
    }
    for (const auto &height : heights) {
        memset(visited, false, sizeof(visited));
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < n; ++j) {
                if (board[i][j] <= height) {
                    visited[i][j] = true;
                }
            }
        }
        int cnt = 0;
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < n; ++j) {
                if (!visited[i][j]) {
                    cnt++;
                    bfs(i, j);
                }
            }
        }
        ans = max(ans, cnt);
    }
    cout << ans << '\n';
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    solve();
    return 0;
}