Submission #962546

#	Time	Username	Problem	Language	Result	Execution time	Memory
962546		alex_2008	Longest Trip (IOI23_longesttrip)	C++17	100 / 100	16 ms	1116 KiB

longesttrip

#include "longesttrip.h"
#include <vector>
#include <iostream>
#include <cmath>
#include <algorithm>
#include <chrono>
#include <random>
using namespace std;
bool find_edge(int a, int b) {
	return are_connected({ a }, { b });
}
vector <int> longest_trip(int n, int d) {
	vector <int> perm(n);
	for (int i = 0; i < n; i++) {
		perm[i] = i;
	}
	mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
	shuffle(perm.begin(), perm.end(), rng);
	vector <int> p1, p2;
	p1.push_back(perm[0]);
	p2.push_back(perm[1]);
	for (int i = 2; i < n - 1; i += 2) {
		int a = perm[i], b = perm[i + 1];
		if (find_edge(a, b)) {
			if (find_edge(p1.back(), a)) {
				p1.push_back(a);
				p1.push_back(b);
			}
			else if (find_edge(p2.back(), a)) {
				p2.push_back(a);
				p2.push_back(b);
			}
			else {
				while (!p2.empty()) {
					p1.push_back(p2.back());
					p2.pop_back();
				}
				p2.push_back(a);
				p2.push_back(b);
			}
		}
		else {
			if (find_edge(p1.back(), a)) p1.push_back(a);
			else {
				p1.push_back(b);
				b = a;
			}
			if (find_edge(p2.back(), b)) {
				p2.push_back(b);
			}
			else {
				while (!p2.empty()) {
					p1.push_back(p2.back());
					p2.pop_back();
				}
				p2.push_back(b);
			}
		}
	}
	if (n % 2 == 1) {
		int a = perm.back();
		if (find_edge(p1.back(), a)) {
			p1.push_back(a);
		}
		else if (find_edge(p2.back(), a)) {
			p2.push_back(a);
		}
		else {
			while (!p2.empty()) {
				p1.push_back(p2.back());
				p2.pop_back();
			}
			p2.push_back(a);
		}
	}
	if (find_edge(p1[0], p2[0])) {
		vector <int> ans;
		reverse(p1.begin(), p1.end());
		for (auto& it : p1) {
			ans.push_back(it);
		}
		for (auto& it : p2) {
			ans.push_back(it);
		}
		return ans;
	}
	if (find_edge(p1[0], p2.back())) {
		vector <int> ans;
		reverse(p1.begin(), p1.end());
		reverse(p2.begin(), p2.end());
		for (auto& it : p1) {
			ans.push_back(it);
		}
		for (auto& it : p2) {
			ans.push_back(it);
		}
		return ans;
	}
	if (find_edge(p1.back(), p2[0])) {
		vector <int> ans;
		for (auto& it : p1) {
			ans.push_back(it);
		}
		for (auto& it : p2) {
			ans.push_back(it);
		}
		return ans;
	}
	if (find_edge(p1.back(), p2.back())) {
		vector <int> ans;
		reverse(p2.begin(), p2.end());
		for (auto& it : p1) {
			ans.push_back(it);
		}
		for (auto& it : p2) {
			ans.push_back(it);
		}
		return ans;
	}
	if (!are_connected(p1, p2)) {
		if ((int)p1.size() > (int)p2.size()) {
			return p1;
		}
		return p2;
	}
	int l = 0, r = (int)p1.size() - 1, ans = -1;
	while (l <= r) {
		int mid = (l + r) / 2;
		vector <int> w;
		for (int i = mid; i < (int)p1.size(); i++) {
			w.push_back(p1[i]);
		}
		if (are_connected(w, p2)) {
			ans = mid;
			l = mid + 1;
		}
		else r = mid - 1;
	}
	int vert1 = ans;
	l = 0; r = (int)p2.size() - 1; ans = -1;
	while (l <= r) {
		int mid = (l + r) / 2;
		vector <int> w;
		for (int i = mid; i < (int)p2.size(); i++) {
			w.push_back(p2[i]);
		}
		if (are_connected({ p1[vert1] }, w)) {
			ans = mid;
			l = mid + 1;
		}
		else r = mid - 1;
	}
	int vert2 = ans;
	vector <int> final_ans;
	for (int i = vert1 + 1; i < (int)p1.size(); i++) {
		final_ans.push_back(p1[i]);
	}
	for (int i = 0; i <= vert1; i++) {
		final_ans.push_back(p1[i]);
	}
	for (int i = vert2; i < (int)p2.size(); i++) {
		final_ans.push_back(p2[i]);
	}
	for (int i = 0; i < vert2; i++) {
		final_ans.push_back(p2[i]);
	}
	return final_ans;
}

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