Submission #962512

#	Time	Username	Problem	Language	Result	Execution time	Memory
962512		alex_2008	Longest Trip (IOI23_longesttrip)	C++17	85 / 100	820 ms	1464 KiB

longesttrip

#include "longesttrip.h"
#include <vector>
#include <iostream>
#include <cmath>
#include <algorithm>
using namespace std;
const int N = 5e2 + 10;
bool used[N];
vector <int> G[N];
vector <int> cur;
bool solved = false;
int f(int v) {
	int cnt = 0;
	for (auto it : G[v]) {
		if (!used[it]) ++cnt;
	}
	return cnt;
}
void dfs(int v, int n) {
	if (solved) return;
	used[v] = true;
	cur.push_back(v);
	if ((int)cur.size() == n) {
		solved = true;
		return;
	}
	int mn_deg = 1000, w = -1;
	for (auto it : G[v]) {
		if (!used[it]) {
			int q = f(it);
			if (q < mn_deg) {
				mn_deg = q;
				w = it;
			}
		}
	}
	if (w != -1) {
		dfs(w, n);
	}
}
bool find_edge(int a, int b) {
	return are_connected({ a }, { b });
}
vector <int> longest_trip(int n, int d) {
	if (d == 3) {
		vector <int> w(n);
		for (int i = 0; i < n; i++) {
			w[i] = i;
		}
		return w;
	}
	if (d == 2) {
		solved = false;
		for (int i = 0; i < n; i++) {
			G[i].clear();
		}
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < i; j++) {
				vector <int> v1, v2;
				v1.push_back(i);
				v2.push_back(j);
				if (are_connected(v1, v2)) {
					G[i].push_back(j);
					G[j].push_back(i);
				}
			}
		}
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < n; j++) {
				used[j] = false;
			}
			dfs(i, n);
			vector <int> ret = cur;
			cur.clear();
			if (solved) {
				return ret;
			}
		}
	}
	vector <int> p1, p2;
	p1.push_back(0);
	p2.push_back(1);
	for (int i = 2; i < n; i++) {
		if (find_edge(p1.back(), i)) {
			p1.push_back(i);
		}
		else if (find_edge(p2.back(), i)) {
			p2.push_back(i);
		}
		else {
			while (!p2.empty()) {
				p1.push_back(p2.back()); 
				p2.pop_back();
			}
			p2.push_back(i);
		}
	}
	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: 45 / 60