Submission #1066034

#	Time	Username	Problem	Language	Result	Execution time	Memory
1066034		pcc	Longest Trip (IOI23_longesttrip)	C++17	15 / 100	867 ms	856 KiB

longesttrip

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

#define vi vector<int>

const int mxn = 300;
 
int ask(vector<int> a,vector<int> b){
	return are_connected(a,b);
}

int dp[mxn][mxn];
bitset<mxn> vis;
int N;

int ask(int a,int b){
	if(dp[a][b] != -1)return dp[a][b];
	return ask(vector<int>({a}),vector<int>({b}));
}

void dfs(int now){
	vis[now] = true;
	for(int i = 0;i<N;i++){
		if(dp[now][i]&&!vis[i])dfs(i);
	}
	return;
}
 
vector<int> get_max_cc(){
	//cerr<<"GETTING MAX CC: "<<endl;
	vector<int> heads;
	vis.reset();
	for(int i = 0;i<N;i++){
		if(!vis[i]){
			heads.push_back(i);
			dfs(i);
		}
	}
	int ans = 0,tar = -1;
	for(auto &i:heads){
		vis.reset();
		dfs(i);
		if(vis.count()>ans){
			ans = vis.count();
			tar = i;
		}
	}
	assert(tar != -1);
	dfs(tar);
	vector<int> re;
	for(int i = 0;i<N;i++)if(vis[i])re.push_back(i);
	return re;
}
 
std::vector<int> longest_trip(int NN, int D){
	N = NN;
	memset(dp,-1,sizeof(dp));
	vis.reset();
	for(int i = 0;i<N;i++){
		dp[i][i] = 1;
		for(int j = i+1;j<N;j++)dp[i][j] = dp[j][i] = ask(i,j);
	}
	dfs(1);
	if(vis.count() != N){
		return get_max_cc();
	}
	deque<int> dq[2];
	set<int> st;
	for(int i = 0;i<N;i++)st.insert(i);
	if(ask(0,1))dq[0] = {0,1};
	else if(ask(1,2))dq[0] = {1,2};
	else dq[0] = {0,2};
	for(auto &i:dq[0])st.erase(i);
 
	while(st.size()){
		if(dq[0].size()<dq[1].size())dq[0].swap(dq[1]);
		//cerr<<*st.begin()<<endl;
		auto now = *st.begin();
		st.erase(now);
		if(ask(now,dq[0].back())){
			dq[0].push_back(now);
			dq[0].swap(dq[1]);
		}
		else{
			dq[1].push_back(now);
		}
		if(dq[0].empty()||dq[1].empty())continue;
		int s = dq[0].front(),t = dq[0].back();
		if(!dp[s][t]){
			if(dp[s][now]){
				while(!dq[1].empty()){
					dq[0].push_front(dq[1].back());
					dq[1].pop_back();
				}
			}
			else if(dp[t][now]){
				while(!dq[1].empty()){
					dq[0].push_back(dq[1].back());
					dq[1].pop_back();
				}
			}
		}
		else{
			assert(dp[s][t]);
			int tar = -1;
			for(auto &i:dq[0]){
				if(dp[i][now])tar = i;
			}
			if(tar == -1)continue;
			while(dq[0][0] != tar){
				dq[0].push_back(dq[0][0]);
				dq[0].pop_front();
			}
			while(!dq[1].empty()){
				dq[0].push_front(dq[1].back());
				dq[1].pop_back();
			}
		}
	}
 
	if(dq[0].size()<dq[1].size())dq[0].swap(dq[1]);
	/*
	cerr<<"DQ: "<<endl;
	for(auto &i:dq[0])cerr<<i<<' ';cerr<<endl;
	for(auto &i:dq[1])cerr<<i<<' ';cerr<<endl;
	cerr<<endl;
	*/
	vector<int> ans;
	for(auto &i:dq[0])ans.push_back(i);
	return ans;
}

Compilation message (stderr)

longesttrip.cpp: In function 'std::vector<int> get_max_cc()':
longesttrip.cpp:44:17: warning: comparison of integer expressions of different signedness: 'std::size_t' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   44 |   if(vis.count()>ans){
      |      ~~~~~~~~~~~^~~~
longesttrip.cpp: In function 'std::vector<int> longest_trip(int, int)':
longesttrip.cpp:65:17: warning: comparison of integer expressions of different signedness: 'std::size_t' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   65 |  if(vis.count() != N){
      |     ~~~~~~~~~~~~^~~~

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