Submission #1065348

#	Time	Username	Problem	Language	Result	Execution time	Memory
1065348		deera	Longest Trip (IOI23_longesttrip)	C++17	15 / 100	7 ms	600 KiB

longesttrip

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

vector<int> solve_d3(int N, int D) {
    vector<int> res(N);
    iota(res.begin(), res.end(), 0);
    return res;
}

vector<int> solve_d2(int N, int D) {
    queue<int> stops;
    for (int i = 1; i < N; i++) stops.push(i);

    deque<int> trip = {0};
    while (stops.size() > 1) {
        int next = stops.front(); stops.pop();
        int last = trip.back();
        
        if (are_connected({next}, {last})) {
            trip.push_back(next);
        } else {
            trip.push_back(stops.front()); stops.pop();
            trip.push_back(next);
        }
    }

    if (stops.size() == 1) {
        int next = stops.front();
        int last = trip.back();
        if (are_connected({next}, {last})) {
            trip.push_back(next);
        } else {
            trip.push_front(stops.front()); stops.pop();
        }
    }

    vector<int> res;
    for (int x : trip) res.push_back(x);
    return res;
}

bool CACHE[256][256];
bool COMPD[256][256];
bool connected(int x, int y) {
    if (x > y) swap(x, y);
    if (COMPD[x][y]) return CACHE[x][y];

    bool res = are_connected({x}, {y});
    CACHE[x][y] = res;
    COMPD[x][y] = true;
    return res;
}

vector<int> longest_trip(int N, int D) {
    if (D == 3) return solve_d3(N, D);
    if (D == 2) return solve_d2(N, D);

    // resetting the cache
    for (auto &row : CACHE) fill(row, row + 256, 0);
    for (auto &row : COMPD) fill(row, row + 256, 0);

    deque<int> trip = {0};

    set<int> stops;
    for (int i = 1; i < N; i++) stops.insert(i);

    int half = (N / 2) + 1;
    int fail = 0;
    while (stops.size() > 1) {
        for (auto next: stops) {
            int a = trip.front(), b = trip.back();

            if (connected(a, next)) {
                trip.push_front(next);
                stops.erase(next);
                fail = 0;
                continue;
            }

            if (connected(b, next)) {
                trip.push_back(next);
                stops.erase(next);
                fail = 0;
                continue;
            }

            if (trip.size() >= half) {
                break;
            }

            fail++;
            CACHE[a][b] = 1;
            CACHE[b][a] = 1;
            COMPD[a][b] = 1;
            COMPD[b][a] = 1;

            if (fail > 100) {
                break;
            }
        }
    }

    vector<int> res;
    for (int x : trip) res.push_back(x);
    return res;
}

Compilation message (stderr)

longesttrip.cpp: In function 'std::vector<int> longest_trip(int, int)':
longesttrip.cpp:88:29: warning: comparison of integer expressions of different signedness: 'std::deque<int, std::allocator<int> >::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   88 |             if (trip.size() >= half) {
      |                 ~~~~~~~~~~~~^~~~~~~

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