Submission #1070611

#	Time	Username	Problem	Language	Result	Execution time	Memory
1070611		Plurm	Longest Trip (IOI23_longesttrip)	C++17	85 / 100	17 ms	856 KiB

longesttrip

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

int dc_left(vector<int> a, vector<int> b) {
    if (a.size() == 1)
        return a.back();
    vector<int> left(a.begin(), a.begin() + a.size() / 2);
    vector<int> right(a.begin() + a.size() / 2, a.end());
    if (are_connected(left, b))
        return dc_left(left, b);
    else
        return dc_left(right, b);
}

int dc_right(vector<int> a, vector<int> b) {
    if (b.size() == 1)
        return b.back();
    vector<int> left(b.begin(), b.begin() + b.size() / 2);
    vector<int> right(b.begin() + b.size() / 2, b.end());
    if (are_connected(a, left))
        return dc_right(a, left);
    else
        return dc_right(a, right);
}

void join(vector<deque<int>> &comp, int u, int v) {
    int a = -1;
    int b = -1;
    for (int i = 0; i < comp.size(); i++) {
        if (!comp[i].empty()) {
            if (comp[i].front() == u) {
                reverse(comp[i].begin(), comp[i].end());
                a = i;
            } else if (comp[i].back() == u) {
                a = i;
            }
            if (comp[i].front() == v) {
                b = i;
            } else if (comp[i].back() == v) {
                reverse(comp[i].begin(), comp[i].end());
                b = i;
            }
        }
    }
    comp[a].insert(comp[a].end(), comp[b].begin(), comp[b].end());
    comp.erase(comp.begin() + b);
}

vector<int> longest_trip(int N, int D) {
    vector<deque<int>> comp(N);
    for (int i = 0; i < N; i++)
        comp[i].push_back(i);
    set<pair<int, int>> known;
    default_random_engine engine;
    engine.seed(time(NULL));
    while (comp.size() > 2) {
        shuffle(comp.begin(), comp.end(), engine);
        int i = 0;
        int j = 1;
        int k = 2;
        int u = comp[i].back();
        int v = comp[j].back();
        int w = comp[k].back();
        if (!known.count(minmax(v, w)) && are_connected({v}, {w})) {
            join(comp, v, w);
        } else if (!known.count(minmax(u, v)) && are_connected({u}, {v})) {
            known.insert(minmax(v, w));
            join(comp, u, v);
        } else {
            known.insert(minmax(u, v));
            known.insert(minmax(v, w));
            join(comp, u, w);
        }
    }
    if (comp[0].size() < comp[1].size()) {
        swap(comp[0], comp[1]);
    }
    if (are_connected({comp[0].back()}, {comp[1].back()})) {
        reverse(comp[1].begin(), comp[1].end());
        comp[0].insert(comp[0].end(), comp[1].begin(), comp[1].end());
    } else if (are_connected({comp[0].back()}, {comp[1].front()})) {
        comp[0].insert(comp[0].end(), comp[1].begin(), comp[1].end());
    } else if (are_connected({comp[0].front()}, {comp[1].front()})) {
        reverse(comp[0].begin(), comp[0].end());
        comp[0].insert(comp[0].end(), comp[1].begin(), comp[1].end());
    } else if (are_connected({comp[0].front()}, {comp[1].back()})) {
        reverse(comp[0].begin(), comp[0].end());
        reverse(comp[1].begin(), comp[1].end());
        comp[0].insert(comp[0].end(), comp[1].begin(), comp[1].end());
    } else if (are_connected(vector<int>(comp[0].begin(), comp[0].end()),
                             vector<int>(comp[1].begin(), comp[1].end()))) {
        // two cycles, connected
        int l = dc_left(vector<int>(comp[0].begin(), comp[0].end()),
                        vector<int>(comp[1].begin(), comp[1].end()));
        int r = dc_right({l}, vector<int>(comp[1].begin(), comp[1].end()));
        int l_idx = find(comp[0].begin(), comp[0].end(), l) - comp[0].begin();
        int r_idx = find(comp[1].begin(), comp[1].end(), r) - comp[1].begin();
        vector<int> ret;
        for (int i = 0; i < comp[0].size(); i++)
            ret.push_back(comp[0][(l_idx + 1 + i) % comp[0].size()]);
        for (int i = 0; i < comp[1].size(); i++)
            ret.push_back(comp[1][(r_idx + i) % comp[1].size()]);
        return ret;
    }
    return vector<int>(comp[0].begin(), comp[0].end());
}

Compilation message (stderr)

longesttrip.cpp: In function 'void join(std::vector<std::deque<int> >&, int, int)':
longesttrip.cpp:30:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::deque<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   30 |     for (int i = 0; i < comp.size(); i++) {
      |                     ~~^~~~~~~~~~~~~
longesttrip.cpp: In function 'std::vector<int> longest_trip(int, int)':
longesttrip.cpp:100:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::deque<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  100 |         for (int i = 0; i < comp[0].size(); i++)
      |                         ~~^~~~~~~~~~~~~~~~
longesttrip.cpp:102:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::deque<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  102 |         for (int i = 0; i < comp[1].size(); i++)
      |                         ~~^~~~~~~~~~~~~~~~

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