Submission #963700

#	Time	Username	Problem	Language	Result	Execution time	Memory
963700		alextodoran	Making Friends on Joitter is Fun (JOI20_joitter2)	C++17	0 / 100	3 ms	15000 KiB

joitter2

/**
 _  _   __  _ _ _  _  _ _
 |a  ||t  ||o    d | |o  |
| __    _| | _ | __|  _ |
| __ |/_  | __  /__\ / _\|

**/

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int N_MAX = 100000;

int N, M;

int root[N_MAX + 2];
int cnt[N_MAX + 2];
set <int> in[N_MAX + 2];
set <int> ins[N_MAX + 2];
set <pair <int, int>> out[N_MAX + 2];
int answer;

int f (int u) {
    return (int) in[u].size() * cnt[u] + cnt[u] * (cnt[u] - 1);
}

int find_root (int u) {
    return (root[u] == 0 ? u : root[u] = find_root(root[u]));
}

vector <pair <int, int>> join_que;

void del_edge (int u, int v) {
    int ru = find_root(u), rv = find_root(v);
    in[rv].erase(u);
    out[u].erase({u, rv});
}
bool add_edge (int u, int v) {
    int ru = find_root(u), rv = find_root(v);
    if (ru == rv || ins[rv].find(ru) != ins[rv].end()) {
        return false;
    }
    in[rv].insert(u);
    out[ru].insert({u, rv});
    ins[rv].insert(ru);
    if (ins[ru].find(rv) != ins[ru].end()) {
        join_que.push_back({ru, rv});
    }
    return true;
}
void join (int u, int v) {
    if (u == v) {
        return;
    }
    if ((int) in[u].size() + (int) out[u].size()
      > (int) in[v].size() + (int) out[v].size()) {
        swap(u, v);
    }
    answer -= f(u) + f(v);
    vector <pair <int, int>> del, add;
    for (int x : in[u]) {
        del.push_back({x, u});
        if (x != v) {
            add.push_back({x, v});
        }
    }
    for (pair <int, int> e : out[u]) {
        del.push_back(e);
        if (e.second != v) {
            add.push_back(e);
        }
    }
    for (pair <int, int> e : del) {
        del_edge(e.first, e.second);
    }
    root[u] = v;
    cnt[v] += cnt[u];
    for (pair <int, int> e : add) {
        add_edge(e.first, e.second);
    }
    answer += f(v);
}

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

    cin >> N >> M;
    fill(cnt + 1, cnt + N + 1, 1);
    while (M--) {
        int u, v;
        cin >> u >> v;
        if (add_edge(u, v) == true) {
            answer += cnt[find_root(v)];
            while (join_que.empty() == false) {
                pair <int, int> e = join_que.back();
                join_que.pop_back();
                join(e.first, e.second);
            }
        }
        cout << answer << "\n";
    }

    return 0;
}

Compilation message (stderr)

joitter2.cpp: In function 'void del_edge(int, int)':
joitter2.cpp:37:9: warning: unused variable 'ru' [-Wunused-variable]
   37 |     int ru = find_root(u), rv = find_root(v);
      |         ^~

• Subtask 1: 0 / 1
• Subtask 2: 0 / 16
• Subtask 3: 0 / 83