Submission #841346

#	Time	Username	Problem	Language	Result	Execution time	Memory
841346		TheLostCookie	Longest Trip (IOI23_longesttrip)	C++17	85 / 100	15 ms	384 KiB

longesttrip

#include "longesttrip.h"
#include <algorithm>
#include <numeric>
#include <vector>

std::vector<int> longest_trip(int N, int D) {
	std::vector<int> l0,l1;
	auto mergeLines = [&l0, &l1]()->void{
		while(!l1.empty()) {
			l0.push_back(l1.back());
			l1.pop_back();
		}
		return;
	};
	
	std::vector<int> p(N);
	std::iota(p.begin(),p.end(),0);
	std::srand(2023);
	std::random_shuffle(p.begin(),p.end());
	
	l0.push_back(p[0]);
	for(int i = 1; i < N; i++) {
		int u = p[i];
		if(l1.empty()) {
			(are_connected({l0.back()},{u})?l0:l1).push_back(u);
		} else {
			if(rand()%2) swap(l0,l1);
			if(!are_connected({l0.back()},{u})) {
				l1.push_back(u);
			} else {
				l0.push_back(u);
				if(are_connected({l1.back()},{u})) {
					mergeLines();
				}
			}
		}
	}
	
	if(l1.empty()) return l0;
	else if(!are_connected(l0,l1)) {
		if(l0.size()>l1.size()) return l0;
		else return l1;
	} else if(l0.size()>1&&(!are_connected({l0.front()},{l0.back()}))) {
		if(!are_connected({l0.back()},{l1.back()})) {
			std::reverse(l0.begin(),l0.end());
		}
		mergeLines();
		return l0;
	} else if(l1.size()>1&&(!are_connected({l1.front()},{l1.back()}))) {
		if(!are_connected({l0.back()},{l1.back()})) {
			std::reverse(l1.begin(),l1.end());
		}
		mergeLines();
		return l0;
	} else {
		std::vector<int> le(l0), ri(l1);
		for(int rep = 0; rep < 2; rep++) {
			while(le.size()>1) {
				std::vector<int> le0,le1;
				for(int i = 0; i < int(le.size()); i++) {
					(i%2?le0:le1).push_back(le[i]);
				}
				if(are_connected(le0,ri)) std::swap(le,le0);
				else std::swap(le,le1);
			}
			swap(le,ri);
		}
		int lei = 0, rii = 0;
		while(l0[lei] != le[0]) lei++;
		while(l1[rii] != ri[0]) rii++;
		
		std::vector<int> ans;
		for(int i = 0; i < int(l0.size()); i++) {
			ans.push_back(l0[(lei+i+1)%l0.size()]);
		}
		for(int i = 0; i < int(l1.size()); i++) {
			ans.push_back(l1[(rii+i)%l1.size()]);
		}
		return ans;
	}
}

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