Submission #1067866

#	Time	Username	Problem	Language	Result	Execution time	Memory
1067866		Plurm	Torrent (COI16_torrent)	C++11	0 / 100	2033 ms	40892 KiB

torrent

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

vector<int> g[300005];
int dep[300005];
vector<int> par[300005];
int chcnt[300005];
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, a, b;
    cin >> n >> a >> b;
    for (int i = 1; i < n; i++) {
        int x, y;
        cin >> x >> y;
        g[x].push_back(y);
        g[y].push_back(x);
    }
    memset(dep, 0x3f, sizeof(dep));
    dep[a] = dep[b] = 0;
    queue<int> q;
    q.push(a);
    q.push(b);
    while (!q.empty()) {
        int u = q.front();
        q.pop();
        for (int v : g[u]) {
            if (dep[v] > dep[u] + 1) {
                dep[v] = dep[u] + 1;
                par[v] = {u};
                q.push(v);
            } else if (dep[v] == dep[u] + 1) {
                par[v].push_back(u);
            }
        }
    }
    priority_queue<pair<int, int>> pq;
    for (int i = 1; i <= n; i++) {
        for (int p : par[i])
            chcnt[p]++;
    }
    for (int i = 1; i <= n; i++) {
        if (chcnt[i] == 0 && i != a && i != b)
            pq.push({dep[i], i});
    }
    int rnd = 0;
    while (!pq.empty()) {
        rnd++;
        vector<int> waitlist;
        set<int> parf;
        while (!pq.empty()) {
            auto p = pq.top();
            pq.pop();
            int chosen = -1;
            for (int pr : par[p.second]) {
                if (!parf.count(pr)) {
                    chosen = pr;
                }
            }
            if (chosen == -1) {
                waitlist.push_back(p.second);
            } else {
                parf.insert(chosen);
                for (int pr : par[p.second]) {
                    chcnt[pr]--;
                }
            }
        }
        for (int u : parf) {
            if (chcnt[u] == 0 && u != 0 && u != a && u != b)
                pq.push({dep[u], u});
        }
        for (int u : waitlist)
            pq.push({dep[u], u});
    }
    cout << rnd << endl;
    return 0;
}

• Subtask 1: 0 / 31
• Subtask 2: 0 / 69