1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
#include <iostream>
#include <vector>
#include <utility>
#include <unordered_set>
#include <queue>

using namespace std;

auto pHash = [](const pair<int, int> & p) { return (size_t)p.first<<32 + (size_t)p.second ^ (size_t)p.first; };

void input(int & n, int & m, int & k, int & q, unordered_set<pair<int, int>, decltype(pHash)> & positions, vector<pair<int, int>> & mods) {
    cin >> n >> m >> k >> q;
    mods.resize(q);
    for(int i = 0; i < k; i++) {
        pair<int, int> cur_pos;
        cin >> cur_pos.first >> cur_pos.second;
        positions.insert(cur_pos);
    }
    for(int i = 0; i < q; i++) {
        cin >> mods[i].first >> mods[i].second;
    }
}

bool can_remove(pair<int, int> const & pos, unordered_set<pair<int, int>, decltype(pHash)> const & positions) {
    return (positions.count({pos.first-1, pos.second}) + positions.count({pos.first+1, pos.second}) == 0)
            || (positions.count({pos.first, pos.second-1}) + positions.count({pos.first, pos.second+1}) == 0);
}

int get_single_result(unordered_set<pair<int, int>, decltype(pHash)> positions) {
    int result = 0;

    queue<pair<int, int>> que;

    vector<pair<int, int>> cand_delta{{1,0},{-1,0},{0,1},{0,-1}};

    for(auto const & pos : positions) {
        if(can_remove(pos, positions)) {
            que.push(pos);
        }
    }

    while(!que.empty()) {
        pair<int, int> cur_pos = que.front();
        que.pop();
        if(!positions.count(cur_pos)) {
            continue;
        }
        positions.erase(cur_pos);
        result++;

        for(auto const & delta : cand_delta) {
            pair<int, int> candidate{cur_pos.first + delta.first, cur_pos.second + delta.second};
            if(positions.count(candidate)) {
                if(can_remove(candidate, positions)) {
                    que.push(candidate);
                }
            }
        }
    }

    return result;
}

void solve() {
    int n, m, k, q;
    unordered_set<pair<int, int>, decltype(pHash)> positions(1000, pHash);
    vector<pair<int, int>> mods;
    input(n, m, k, q, positions, mods);

    cout << get_single_result(positions) << "\n";

    for(auto const & mod : mods) {
        if(positions.count(mod)) {
            positions.erase(mod);
        } else {
            positions.insert(mod);
        }
        cout << get_single_result(positions) << "\n";
    }
}

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    solve();

    return 0;
}