Submission #1004819

#	Time	Username	Problem	Language	Result	Execution time	Memory
1004819		thinknoexit	Longest Trip (IOI23_longesttrip)	C++17	85 / 100	16 ms	692 KiB

longesttrip

#include <bits/stdc++.h>
#include "longesttrip.h"
using namespace std;
using ll = long long;
int n;
vector<int> longest_trip(int N, int D) {
    n = N;
    vector<int> Permu(n, 0);
    iota(Permu.begin(), Permu.end(), 0);
    random_shuffle(Permu.begin(), Permu.end());
    vector<int> p1, p2;
    p1.push_back(Permu[0]);
    bool ok = 1;
    for (int _i = 1;_i < n;_i++) {
        int i = Permu[_i];
        if (p2.empty()) {
            if (are_connected({ p1.back() }, { i })) p1.push_back(i);
            else p2.push_back(i);
        }
        else {
            if (are_connected({ p1.back() }, { p2.back(), i })) {
                p1.push_back(i);
                if (are_connected({ p1.back() }, { p2.back() })) {
                    reverse(p2.begin(), p2.end());
                    for (auto& x : p2) p1.push_back(x);
                    p2.clear();
                }
            }
            else {
                p2.push_back(i);
            }
        }
    }
    if (p1.size() > p2.size()) swap(p1, p2);
    if ((int)p2.size() == n) return p2;
    int l = 0, r = p1.size();
    while (l < r) {
        int mid = (l + r) / 2;
        vector<int> t;
        for (int j = 0;j <= mid;j++) t.push_back(p1[j]);
        if (are_connected(t, p2)) r = mid;
        else l = mid + 1;
    }
    if (l == (int)p1.size()) return p2;
    if (are_connected({ p1.back() }, p2)) {
        reverse(p1.begin(), p1.end());
    }
    else {
        vector<int> p3;
        for (int i = 0;i < (int)p1.size();i++) {
            p3.push_back(p1[(i + l) % ((int)p1.size())]);
        }
        swap(p1, p3);
    }
    l = 0, r = p2.size() - 2;
    while (l < r) {
        int mid = (l + r) / 2;
        vector<int> t;
        for (int j = 0;j <= mid;j++) t.push_back(p2[j]);
        if (are_connected(t, { p1.front() })) r = mid;
        else l = mid + 1;
    }
    if (are_connected({ p1.front() }, { p2.back() })) {
        vector<int> ans;
        for (auto& x : p2) ans.push_back(x);
        for (auto& x : p1) ans.push_back(x);
        return ans;
    }
    else {
        vector<int> p3;
        for (int i = 0;i < (int)p2.size();i++) {
            p3.push_back(p2[(i + l) % ((int)p2.size())]);
        }
        swap(p2, p3);
    }
    reverse(p2.begin(), p2.end());
    vector<int> ans;
    for (auto& x : p2) ans.push_back(x);
    for (auto& x : p1) ans.push_back(x);
    return ans;
}

Compilation message (stderr)

longesttrip.cpp: In function 'std::vector<int> longest_trip(int, int)':
longesttrip.cpp:13:10: warning: unused variable 'ok' [-Wunused-variable]
   13 |     bool ok = 1;
      |          ^~

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