Submission #878687

#	Time	Username	Problem	Language	Result	Execution time	Memory
878687		SanguineChameleon	Longest Trip (IOI23_longesttrip)	C++17	25 / 100	7 ms	616 KiB

longesttrip

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

vector<int> longest_trip(int N, int D) {
	vector<int> rem(N);
	iota(rem.rbegin(), rem.rend(), 0);
	vector<int> path1;
	vector<int> path2;
	while (!rem.empty()) {
		int u = rem.back();
		rem.pop_back();
		if (path1.empty()) {
			path1.push_back(u);
			continue;
		}
		if (path2.empty()) {
			path2.push_back(u);
			continue;
		}
		if (rem.empty()) {
			if (are_connected({path1.back()}, {u})) {
				path1.push_back(u);
				continue;
			}
			if (are_connected({path2.back()}, {u})) {
				path2.push_back(u);
				continue;
			}
			path1.insert(path1.end(), path2.rbegin(), path2.rend());
			path2 = {u};
			continue;
		}
		int v = rem.back();
		rem.pop_back();
		if (are_connected({u}, {v})) {
			if (are_connected({path1.back()}, {u})) {
				path1.push_back(u);
				path1.push_back(v);
				continue;
			}
			if (are_connected({path2.back()}, {u})) {
				path2.push_back(u);
				path2.push_back(v);
				continue;
			}
			path1.insert(path1.end(), path2.rbegin(), path2.rend());
			path2 = {u, v};
		}
		else {
			int nxt1 = (are_connected({path1.back()}, {u}) ? u : v);
			int nxt2 = (are_connected({path2.back()}, {u}) ? u : v);
			if (nxt1 == nxt2) {
				path1.push_back(nxt1);
				path1.insert(path1.end(), path2.rbegin(), path2.rend());
				path2 = {u ^ v ^ nxt1};
			}
			else {
				path1.push_back(nxt1);
				path2.push_back(nxt2);
			}
		}
	}
	if (path1.empty()) {
		return path2;
	}
	if (path2.empty()) {
		return path1;
	}
/*	vector<pair<int, int>> ends = {{path1[0], path2[0]}, {path1.back(), path2[0]}, {path1[0], path2.back()}};
	for (auto [u, v]: ends) {
		if (are_connected({u}, {v})) {
			if (path1.back() != u) {
				reverse(path1.begin(), path1.end());
			}
			if (path2[0] != v) {
				reverse(path2.begin(), path2.end());
			}
			path1.insert(path1.end(), path2.begin(), path2.end());
			return path1;
		}
	}
	if (!are_connected(path1, path2)) {*/
		if (path1.size() > path2.size()) {
			return path1;
		}
		else {
			return path2;
		}
	//}
	vector<int> cand1 = path1;
	vector<int> cand2 = path2;
	for (int iter = 0; iter < 2; iter++) {
		while ((int)cand1.size() > 1) {
			vector<int> left_cand(cand1.begin(), cand1.begin() + (int)cand1.size() / 2);
			vector<int> right_cand(cand1.begin() + (int)cand1.size() / 2, cand1.end());
			if (are_connected(left_cand, cand2)) {
				cand1.swap(left_cand);
			}
			else {
				cand1.swap(right_cand);
			}
		}
		cand1.swap(cand2);
	}
	rotate(path1.begin(), path1.end(), find(path1.begin(), path1.end(), cand1[0]));
	rotate(path2.begin(), path2.end(), find(path2.begin(), path2.end(), cand2[0]));
	path1.insert(path1.begin(), path2.rbegin(), path2.rend());
	return path1;
}

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