[USACO21FEB] Comfortable Cows S

#include <bits/stdc++.h>

using namespace std;
const int MAX_NUM = 5005;
bool have_cow[MAX_NUM][MAX_NUM];
int cow[MAX_NUM][MAX_NUM], ans;

int cx[4] = {0, 0, 1, -1};
int cy[4] = {1, -1, 0, 0};

pair<int, int> check(int x, int y) {
    for (int i = 0; i < 4; ++i) {
        if (!have_cow[x + cx[i]][y + cy[i]]) {
            return {x + cx[i], y + cy[i]};
        }
    }
}

void dfs(int x, int y) {
    if (!have_cow[x][y]) {
        return;
    }
    int cnt = 0;
    for (int i = 0; i < 4; ++i) {
        if (have_cow[x + cx[i]][y + cy[i]]) {
            ++cnt;
        }
    }

    if (cnt == 3) {
        pair<int, int> k = check(x, y);
        have_cow[k.first][k.second] = true;
        ++ans;
        dfs(k.first, k.second);
        for (int i = 0; i < 4; ++i) {
            dfs(k.first + cx[i], k.second + cy[i]);
        }
    }
}

void best_coder() {
    int n;
    cin >> n;
    for (int i = 0; i < n; ++i) {
        int x, y;
        cin >> x >> y;
        x += 1000;
        y += 1000;
        if (have_cow[x][y]) {
            --ans;
            cout << ans << '\n';
            continue;
        }
        have_cow[x][y] = true;
        dfs(x, y);
        for (int j = 0; j < 4; ++j) {
            dfs(x + cx[j], y + cy[j]);
        }
        cout << ans << '\n';
    }
}

void happy_coder() {

}

int main() {
    // ÌáÉýcin¡¢coutЧÂÊ
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    // СÂë½³
    best_coder();

    // ×îÓŽâ
    // happy_coder();

    return 0;
}