Submission #843020

#	Time	Username	Problem	Language	Result	Execution time	Memory
843020		pit4h	Longest Trip (IOI23_longesttrip)	C++17	85 / 100	13 ms	956 KiB

longesttrip

#include<bits/stdc++.h>
#include "longesttrip.h"

using namespace std;

pair<int, int> find_connection(vector<int> vec1, vector<int> vec2) {
    if (!are_connected(vec1, vec2)) {
        return make_pair(-1, -1);
    }
    if (vec1.size() == 1 && vec2.size() == 1) {
        return make_pair(vec1[0], vec2[0]);
    } 
    if (vec1.size() == 1) {
        pair<int, int> res = find_connection(vec2, vec1);
        return make_pair(res.second, res.first);
    }

    vector<int> half;
    for (int i = 0; i < (int)vec1.size() / 2; i++) {
        half.push_back(vec1[i]);
    }
    pair<int, int> res = find_connection(half, vec2);
    if (res != make_pair(-1, -1)) {
        return res;
    }

    half.clear();
    for (int i = (int)vec1.size() / 2; i < (int)vec1.size(); i++) {
        half.push_back(vec1[i]);
    }
    return find_connection(half, vec2);
}

int find_position(int el, vector<int> vec) {
    for (int i = 0; i < (int)vec.size(); i++) {
        if (vec[i] == el) {
            return i;
        }
    }
    return -1;
}

vector<int> longest_trip(int N, int D)
{
    mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
    vector<int> path[2];  

    path[0] = {0}; 

    for (int i = 1; i < N; i++) {
        bool which = uniform_int_distribution<int>(0, 1)(rng);
        if (path[which].empty()) {
            which = !which;
        }

        if (are_connected({path[which].back()}, {i})) {
            path[which].push_back(i);
            if (!path[!which].empty() && 
                are_connected({path[!which].back()}, {i})) {
                while (!path[!which].empty()) {
                    path[which].push_back(path[!which].back());
                    path[!which].pop_back();
                }        
            }
        }
        else {
            path[!which].push_back(i);
        }
    }

    if (path[0].empty()) {
        return path[1];
    }
    if (path[1].empty()) {
        return path[0];
    }

    vector<int> res;
    vector<int> path_ends[2];

    for (int i = 0; i <= 1; i++) {
        if (path[i].size() == 1u) {
            path_ends[i] = {path[i][0]};
        }
        else {
            path_ends[i] = {path[i][0], path[i].back()};
        }
    }

    if (are_connected(path_ends[0], path_ends[1])) {
        if (are_connected({path[0][0]}, {path[1][0]})) {
            for (int i: path[1]) {
                res.push_back(i);
            }
            reverse(res.begin(), res.end());
            for (int i: path[0]) {
                res.push_back(i);
            }
        }
        else if(are_connected({path[0][0]}, {path[1].back()})) {
            for (int i: path[1]) {
                res.push_back(i);
            }
            for (int i: path[0]) {
                res.push_back(i);
            }
        }
        else if(are_connected({path[0].back()}, {path[1][0]})) {
            for (int i: path[0]) {
                res.push_back(i);
            }
            for (int i: path[1]) {
                res.push_back(i);
            }
        }
        else {
            assert(false);
        }
    }
    else {
        pair<int, int> conn = find_connection(path[0], path[1]);
        if (conn == make_pair(-1, -1)) {
            res = (path[0].size() > path[1].size())?path[0] : path[1];
        }
        else {
            int pos[2] = {find_position(conn.first, path[0]), find_position(conn.second, path[1])};
            for (int i = (pos[0] + 1) % path[0].size(); i != pos[0]; i = (i + 1) % path[0].size()) {
                res.push_back(path[0][i]);
            }        
            res.push_back(conn.first);
            res.push_back(conn.second);
            for (int i = (pos[1] + 1) % path[1].size(); i != pos[1]; i = (i + 1) % path[1].size()) {
                res.push_back(path[1][i]);
            }
        }
    }

    return res;
}

• Subtask 0: 0 / 0
• Subtask 1: 5 / 5
• Subtask 2: 10 / 10
• Subtask 3: 25 / 25
• Subtask 4: 45 / 60