Submission #994386

#	Time	Username	Problem	Language	Result	Execution time	Memory
994386		gmroh06	우호 조약 체결 (JOI14_friends)	C++14	100 / 100	79 ms	11932 KiB

friends

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

inline void fastio() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);
    std::cout.tie(nullptr);
}

ll n, m, ans;
ll parent[101010], cnt[101010];
bool vst[101010];
vector<ll> gr[101010];
queue<ll> q;

ll Find(ll x) {
    if (x == parent[x]) {
        return x;
    } else {
        return parent[x] = Find(parent[x]);
    }
}

void Union(ll x, ll y) {
    parent[Find(y)] = Find(x);
}

int main() {
    fastio();

    cin >> n >> m;

    for (ll i = 0, a, b; i < m; i++) {
        cin >> a >> b;

        gr[a].emplace_back(b);
    }

    for (ll i = 1; i <= n; i++) {
        parent[i] = i;
    }

    for (ll i = 1; i <= n; i++) {
        if (vst[i] or gr[i].size() < 2) continue;

        vector<ll> p;
        q.emplace(i);

        while (!q.empty()) {
            ll loc = q.front();
            q.pop();

            if (vst[loc]) continue;

            vst[loc] = true;

            for (auto& x : gr[loc]) {
                p.emplace_back(x);
                q.emplace(x);
            }
        }

        for (ll j = 0; j < p.size() - 1; j++) {
            Union(p[j], p[j + 1]);
        }

        vst[i] = false;
    }

    for (ll i = 1; i <= n; i++) {
        cnt[Find(i)]++;
    }

    for (ll i = 1; i <= n; i++) {
        ans += cnt[i] * (cnt[i] - 1);
    }

    for (ll i = 1; i <= n; i++) {
        for (auto& x : gr[i]) {
            ans += Find(x) != Find(i);
        }
    }

    cout << ans;

    return 0;
}

Compilation message (stderr)

friends.cpp: In function 'int main()':
friends.cpp:65:26: warning: comparison of integer expressions of different signedness: 'll' {aka 'long long int'} and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   65 |         for (ll j = 0; j < p.size() - 1; j++) {
      |                        ~~^~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 30 / 30
• Subtask 3: 65 / 65