Submission #1232999

#	Time	Username	Problem	Language	Result	Execution time	Memory
1232999		LaMatematica14	Star Trek (CEOI20_startrek)	C++20	38 / 100	65 ms	18244 KiB

startrek

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

const long long mod = 1000000007;

int main() {
    long long N, D; cin >> N >> D;
    vector<vector<long long>> adj(N+1); // occhio 1-based
    for (long long  i = 0; i < N-1; i++) {
        long long u, v; cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    vector<long long> nl(N+1, 0); // count number of loosing from there
    function<void(long long,long long)> dfs = [&](long long a, long long p) {
        for (long long x : adj[a]) {
            if (x == p) continue;
            dfs(x, a);
            if (nl[x] == 0) nl[a]++;
        }
    };

    vector<long long> w(N+1, 0); // is this a winning root?
    function<void(long long,long long)> decroot = [&](long long a, long long p) {
        if (w[p] == 0) nl[a]++;
        else if (nl[a] == 0 && nl[p] == 1) nl[a]++;
        if (nl[a] > 0) w[a] = 1;
        for (long long x : adj[a]) {
            if (x == p) continue;
            decroot(x, a);
        }
    };

    long long swappable = 0;
    function<void(long long, long long)> cswap = [&](long long a, long long p) {
        if (nl[a] > 1) return;
        if (nl[a] == 0) {
            swappable++;
            for (long long x : adj[a]) {
                if (x == p) continue;
                cswap(x, a);
            }
        }
        else {
            for (long long x : adj[a]) {
                if (x == p || nl[x] > 0) continue;
                cswap(x, a);
            }
        }
    };

    dfs(1, 0);
    long long ln = 0;
    for (long long i = 1; i <= N; i++) ln += ((nl[i] == 0) ? 1 : 0); 
    long long wn = N-ln;
    cswap(1, 0);
    w[1] = nl[1] > 0;
    for (long long x : adj[1]) decroot(x, 1);
    long long wr = 0;
    for (long long i = 1; i <= N; i++) wr += (w[i] ? 1 : 0); 
    

    long long tot = 0;
    if (w[1]) { // non cambio nulla
        tot += wn*N;
        tot += (ln-swappable)*N;
        tot += swappable*wr;
    } else {
        tot += swappable*(N-wr);
    }
    cout << tot%mod << "\n";
}

• Subtask 1: 0 / 0
• Subtask 2: 0 / 7
• Subtask 3: 8 / 8
• Subtask 4: 15 / 15
• Subtask 5: 15 / 15
• Subtask 6: 0 / 20
• Subtask 7: 0 / 20
• Subtask 8: 0 / 15