Submission #128430

#	Time	Username	Problem	Language	Result	Execution time	Memory
128430		TadijaSebez	Triangles (CEOI18_tri)	C++11	100 / 100	32 ms	2160 KiB

tri

#include "trilib.h"
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
bool comp(int i, int j){ return is_clockwise(1,i,j);}
int main()
{
	int n=get_n();
	vector<int> v[2]={{2},{2}},u[2];
	for(int i=3;i<=n;i++) v[is_clockwise(1,2,i)].pb(i);
	for(int t=0;t<2;t++)
	{
		sort(v[t].begin(),v[t].end(),comp);
		for(int i:v[t])
		{
			while(u[t].size()>1 && !is_clockwise(u[t][u[t].size()-2],u[t].back(),i)) u[t].pop_back();
			u[t].pb(i);
		}
		if(t) reverse(u[t].begin(),u[t].end());
		u[t].insert(u[t].begin(),1);
	}
	if(min(u[0].size(),u[1].size())==2)
	{
		give_answer(max(u[0].size(),u[1].size()));
		return 0;
	}
	for(int t=0;t<2;t++)
	{
		u[0].pop_back();
		while(1)
		{
			bool ok=0;
			if(u[0].size()>1 && !is_clockwise(u[0][u[0].size()-2],u[0].back(),u[1].back())) u[0].pop_back(),ok=1;
			if(u[1].size()>1 && !is_clockwise(u[0].back(),u[1].back(),u[1][u[1].size()-2])) u[1].pop_back(),ok=1;
			if(!ok) break;
		}
		reverse(u[0].begin(),u[0].end());
		reverse(u[1].begin(),u[1].end());
		swap(u[0],u[1]);
	}
	give_answer(u[0].size()+u[1].size());
	return 0;
}

• Subtask 1: 15 / 15
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 20 / 20
• Subtask 5: 25 / 25