Submission #1077260

#	Time	Username	Problem	Language	Result	Execution time	Memory
1077260		emptypringlescan	Longest Trip (IOI23_longesttrip)	C++17	85 / 100	14 ms	856 KiB

longesttrip

#include <bits/stdc++.h>
using namespace std;
#include "longesttrip.h"
vector<int> longest_trip(int n, int d){
	assert(d>0);
	vector<vector<int> > chains;
	for(int i=0; i<n; i++) chains.push_back({i});
	mt19937 rng(999);
	shuffle(chains.begin(),chains.end(),rng);
	while((int)chains.size()>2){
		vector<int> take[3];
		for(int i=0; i<3; i++){
			swap(take[i],chains[(int)chains.size()-i-1]);
		}
		chains.pop_back();
		if(are_connected({take[0][0]},{take[2][0]})) swap(take[1],take[2]);
		else if(are_connected({take[1][0]},{take[2][0]})) swap(take[0],take[2]);
		reverse(take[0].begin(),take[0].end());
		for(int i:take[1]) take[0].push_back(i);
		take[1].clear();
		swap(chains[(int)chains.size()-1],take[0]);
		swap(chains[(int)chains.size()-2],take[2]);
	}
	assert((int)chains.size()==2);
	if(are_connected(chains[0],chains[1])){
		int lo=0,hi=chains[1].size()-1,mid;
		vector<int> hehe;
		while(lo<hi){
			hehe.clear();
			mid=(lo+hi)/2;
			for(int i=lo; i<=mid; i++) hehe.push_back(chains[1][i]);
			if(are_connected(chains[0],hehe)) hi=mid;
			else lo=mid+1;
		}
		int m2=chains[1][lo];
		lo=0,hi=chains[0].size()-1;
		while(lo<hi){
			hehe.clear();
			mid=(lo+hi)/2;
			for(int i=lo; i<=mid; i++) hehe.push_back(chains[0][i]);
			if(are_connected({m2},hehe)) hi=mid;
			else lo=mid+1;
		}
		int m1=chains[0][lo];
		if(m2!=chains[1][0]&&m2!=chains[1].back()){
			if(are_connected({m1},{chains[1].back()})){
				reverse(chains[1].begin(),chains[1].end());
			}
			else if(are_connected({chains[1][0]},{chains[1].back()})){
				hehe.clear();
				while(!chains[1].empty()){
					if(chains[1].back()==m2) break;
					hehe.push_back(chains[1].back());
					chains[1].pop_back();
				}
				reverse(chains[1].begin(),chains[1].end());
				for(int i:hehe) chains[1].push_back(i);
			}
		}
		else if(m2==chains[1].back()) reverse(chains[1].begin(),chains[1].end());
		if(m1==chains[0].back()){
			for(int i:chains[1]) chains[0].push_back(i);
			return chains[0];
		}
		else if(m1==chains[0][0]){
			reverse(chains[0].begin(),chains[0].end());
			for(int i:chains[1]) chains[0].push_back(i);
			return chains[0];
		}
		else{
			if(are_connected({chains[0][0]},{chains[1].back()})){
				for(int i:chains[0]) chains[1].push_back(i);
				return chains[1];
			}
			else if(are_connected({chains[0].back()},{chains[1].back()})){
				reverse(chains[1].begin(),chains[1].end());
				for(int i:chains[1]) chains[0].push_back(i);
				return chains[0];
			}
			else{
				hehe.clear();
				while(!chains[0].empty()){
					if(chains[0].back()==m1) break;
					hehe.push_back(chains[0].back());
					chains[0].pop_back();
				}
				vector<int> ans;
				while(!hehe.empty()){
					ans.push_back(hehe.back());
					hehe.pop_back();
				}
				for(int i:chains[0]) ans.push_back(i);
				for(int i:chains[1]) ans.push_back(i);
				return ans;
			}
		}
	}
	else{
		if(chains[0].size()>chains[1].size()) return chains[0];
		else return chains[1];
	}
}

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