Submission #1037926

#	Time	Username	Problem	Language	Result	Execution time	Memory
1037926		Zicrus	Longest Trip (IOI23_longesttrip)	C++17	40 / 100	906 ms	1572 KiB

longesttrip

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

typedef long long ll;

vector<vector<ll>> adj;
vector<ll> dist;
vector<bool> vst;
ll numVst;

void dfs1(ll cur, ll depth) {
    dist[cur] = depth;
    vst[cur] = true;
    numVst++;
    for (auto &e : adj[cur]) {
        if (!vst[e]) dfs1(e, depth+1);
    }
}

void dfs2(ll cur, ll depth) {
    dist[cur] = depth;
    vst[cur] = true;
    for (auto &e : adj[cur]) {
        if (!vst[e]) dfs2(e, depth+1);
    }
}

vector<int> longest_trip(int n, int d) {
    adj = vector<vector<ll>>(n);
    for (int i = 0; i < n; i++) {
        for (int j = i+1; j < n; j++) {
            if (are_connected({i}, {j})) {
                adj[i].push_back(j);
                adj[j].push_back(i);
            }
        }
    }

    dist = vector<ll>(n);
    vst = vector<bool>(n);
    numVst = 0;
    dfs1(0, 0);
    ll start = 0;
    if (numVst <= n/2) {
        for (int i = 0; i < n; i++) {
            if (!vst[i]) {
                start = i;
                break;
            }
        }
    }
    else {
        ll mx = 0;
        for (int i = 0; i < n; i++) {
            if (dist[i] > mx) {
                start = i;
                mx = dist[i];
            }
        }
    }
    dist = vector<ll>(n);
    vst = vector<bool>(n);
    dfs2(start, 0);

    ll cur = 0;
    ll mx = 0;
    for (int i = 0; i < n; i++) {
        if (dist[i] > mx) {
            cur = i;
            mx = dist[i];
        }
    }
    vector<int> res = {(int)cur};
    while (dist[cur]) {
        for (auto &e : adj[cur]) {
            if (dist[e] == dist[cur]-1) {
                cur = e;
                res.push_back(e);
                break;
            }
        }
    }
    return res;
}

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