Submission #1214274

#	Time	Username	Problem	Language	Result	Execution time	Memory
1214274		ByeWorld	Triangles (CEOI18_tri)	C++20	75 / 100	2065 ms	271748 KiB

tri

#include "trilib.h"
#include <bits/stdc++.h>
// #pragma GCC optimize("O3")
#define ll long long
#define se second
#define fi first
#define pb push_back
#define lf (id<<1)
#define rg ((id<<1)|1)
#define md ((l+r)>>1)
using namespace std;
typedef pair<ll,ll> pii;
typedef pair<int,pii> ipii;
typedef pair<pii,int> piii;
const int MAXN = 1e7+10;
const int SQRT = 450;
const int INF = 1e9+10;
const int MOD = 998244353;
const int LOG = 30;

int n;
vector<int> up, dw, urut;
int que;
map<array<int,3>, int> ma;
 
bool clock(int x, int y, int z){
	if(ma.find({x,y,z}) != ma.end()) return ma[{x,y,z}];

	que++;
	if(que >= 720'000) assert(false);
	bool ret = is_clockwise(x,y,z);
	ma[{x,y,z}] = ma[{y,z,x}] = ma[{z,x,y}] = ret;
	ma[{x,z,y}] = ma[{z,y,x}] = ma[{y,x,z}] = 1-ret;
	return ret;
}
bool cmp(int a, int b){
	if(clock(2, a, b)) return 1;
	return 0;
}

vector<int> ANS;
void solve(){
	ANS.clear();
	ANS.pb(urut[0]); ANS.pb(urut[1]);
	for(int i=2; i<urut.size(); i++){
		while(ANS.size()>=2 && !clock(
			ANS[ANS.size()-2], ANS.back(), urut[i]) ) ANS.pop_back();

		ANS.pb(urut[i]);
	}

	bool done = 0;
	while(!done){
		done = 1;
		while(ANS.size() > 3 && 
			!clock( ANS.back(), ANS[0], ANS[1]) ){

			vector<int> vec;
			for(int j=1; j<ANS.size(); j++){
				vec.pb(ANS[j]);
			}
			ANS = vec;
			done = 0; break;
		}
		if(!done) continue;

		while(ANS.size() > 3 && 
			!clock(ANS[ANS.size()-2], ANS.back(), ANS[0]) ){

			vector<int> vec;
			for(int j=0; j+1<ANS.size(); j++){
				vec.pb(ANS[j]);
			}
			ANS = vec;
			done = 0; break;
		}
	}

}
signed main(){
	n = get_n();
	if(n==3){ give_answer(n); exit(0); }

	for(int i=3; i<=n; i++){
		if(clock(1, 2, i)) dw.pb(i);
		else up.pb(i);
	}
	sort(dw.begin(), dw.end(), cmp);
	sort(up.begin(), up.end(), cmp);

	// for(auto in : up) cout << in << " up\n";
	// for(auto in : dw) cout << in << " dw\n";

	urut.pb(1);
	for(auto in : up) urut.pb(in);
	urut.pb(2);
	for(auto in : dw) urut.pb(in);

	solve();

	give_answer((int)ANS.size());
}

• Subtask 1: 15 / 15
• Subtask 2: 20 / 20
• Subtask 3: 20 / 20
• Subtask 4: 20 / 20
• Subtask 5: 0 / 25