Submission #1080988

#	Time	Username	Problem	Language	Result	Execution time	Memory
1080988		asdasdqwer	Longest Trip (IOI23_longesttrip)	C++17	40 / 100	910 ms	2032 KiB

longesttrip

#pragma GCC optimize("O3")
#pragma GCC target("avx,avx2,sse4")

#include "longesttrip.h"

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

std::vector<int> longest_trip(int N, int D) {
    vector<vector<int>> g(N);
    if (D == 3) {
        vector<int> v;
        for (int i=0;i<N;i++) {
            v.push_back(i);
        }
        return v;
    }

    vector<array<int,2>> pr((N*(N-1))/2);
    int cnt=0;
    for (int i=0;i<N;i++) {
        for (int j=i+1;j<N;j++) {
            pr[cnt++] = {i, j};
        }
    }

    mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
    // shuffle(pr.begin(), pr.end(), rng);
    
    for (auto [i, j] : pr) {
        if (are_connected({i}, {j})) {
            g[i].push_back(j);
            g[j].push_back(i);
        }
    }

    vector<bool> vv(N, false);
    function<void(int)> df=[&](int node) {
        vv[node]=true;
        for (int &x:g[node]) {
            if (!vv[x]) df(x);
        }
    };
    df(0);
    for (int i=0;i<N;i++) {
        if (!vv[i]) {
            vector<int> f1, f2;
            for (int j=0;j<N;j++) {
                if (vv[j])f1.push_back(j);
                else f2.push_back(j);
            }
            if (f1.size() > f2.size()) return f1;
            return f2;
        }
    }


    vector<int> lng;

    int hf = N/2;
    if (N%2 != 0) hf++;

    for (int i=0;i<N;i++) {
        vector<int> tmp;
        vector<bool> vis(N, false);
        function<void(int)> dfs=[&](int node) {
            vis[node] =  true;
            tmp.push_back(node);

            if (lng.size() < tmp.size()) lng = tmp;

            for (int x:g[node]) {
                if (!vis[x]) {
                    dfs(x);
                }
            }

            tmp.pop_back();
        };

        dfs(i);

        if (lng.size() < tmp.size()) {
            lng = tmp;
        }

        if ((D == 2 && (int)lng.size() == N) || (D == 1 && (int)lng.size() >= hf)) return lng;
    }

    return lng;
}

• Subtask 0: 0 / 0
• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 25 / 25
• Subtask 4: 0 / 60