Submission #1016452

#	Time	Username	Problem	Language	Result	Execution time	Memory
1016452		pavement	Longest Trip (IOI23_longesttrip)	C++17	15 / 100	195 ms	600 KiB

longesttrip

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

#define pb push_back

vector<int> longest_trip(int N, int D) {
	vector<int> ret;
	if (D == 3) {
		ret.resize(N);
		iota(ret.begin(), ret.end(), 0);
	} else if (D == 2) {
		deque<int> dq;
		int st = -1;
		dq.pb(0);
		if (are_connected({0}, {1})) {
			dq.pb(1);
			st = 2;
		} else {
			dq.pb(2);
			dq.pb(1);
			st = 3;
		}
		for (int i = st; i < N; i++) {
			if (are_connected({i}, {dq.back()})) {
				dq.pb(i);
			} else {
				dq.push_front(i);
			}
		}
		ret = vector<int>(dq.begin(), dq.end());
	} else {
		deque<int> ch1, ch2;
		ch1.pb(0);
		int i = 1;
		for (; i < N; i++) {
			vector<int> tmp;
			if (ch1.size() == 1) {
				tmp.pb(ch1.front());
			} else {
				tmp.pb(ch1.front());
				tmp.pb(ch1.back());
			}
			if (are_connected(tmp, {i})) {
				if (are_connected({ch1.front()}, {i})) {
					ch1.push_front(i);
				} else {
					ch1.pb(i);
				}
			} else {
				ch2.pb(i);
				break;
			}
		}
		for (i++; i < N; i++) {
			if (are_connected({ch1.back()}, {i})) {
				ch1.pb(i);
				if (ch2.size() == 1) {
					if (are_connected({ch2.back()}, {i})) {
						ch1.pb(ch2.back());
						ch2.pop_back();
					}
				} else if (!ch2.empty()) {
					if (are_connected({ch2.front(), ch2.back()}, {i})) {
						if (are_connected({ch2.back()}, {i})) {
							while (!ch2.empty()) {
								ch1.pb(ch2.back());
								ch2.pop_back();
							}
						} else {
							while (!ch2.empty()) {
								ch1.pb(ch2.front());
								ch2.pop_front();
							}
						}
					}
				}
			} else {
				ch2.pb(i);
				if (are_connected({ch1.front()}, {i})) {
					while (!ch2.empty()) {
						ch1.push_front(ch2.back());
						ch2.pop_back();
					}
				}
			}
		}
		vector<int> vec1(ch1.begin(), ch1.end()), vec2(ch2.begin(), ch2.end());
		if (!vec1.empty() && !vec2.empty() && are_connected(vec1, vec2)) {
			int lo = 0, hi = (int)vec1.size() - 1, idx1 = -1;
			while (lo <= hi) {
				int mid = (lo + hi) / 2;
				if (are_connected(vector<int>(vec1.begin() + lo, vec1.begin() + mid + 1), vec2)) {
					idx1 = i;
					hi = mid - 1;
				} else {
					lo = mid;
				}
			}
			assert(idx1 != -1);
			lo = 0, hi = (int)vec2.size() - 1;
			int idx2 = -1;
			while (lo <= hi) {
				int mid = (lo + hi) / 2;
				if (are_connected(vector<int>(vec2.begin() + lo, vec2.begin() + mid + 1), {idx1})) {
					idx2 = i;
					hi = mid - 1;
				} else {
					lo = mid;
				}
			}
			assert(idx2 != -1);
			// vec1[idx1] and vec2[idx2] are connected
			for (int i = (idx1 + 1) % (int)vec1.size(); i != idx1; i = (i + 1) % (int)vec1.size()) {
				ret.pb(vec1[i]);
			}
			for (int i = idx2; (int)ret.size() != N; i = (i + 1) % (int)vec2.size()) {
				ret.pb(vec2[i]);
			}
		} else {
			if (vec1.size() > vec2.size()) {
				ret = vec1;
			} else {
				ret = vec2;
			}
		}
	}
	return ret;
}

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