Submission #1229466

#	Time	Username	Problem	Language	Result	Execution time	Memory
1229466		radodododo	Triangles (CEOI18_tri)	C++20	75 / 100	23 ms	1604 KiB

tri

#include <iostream>
#include <vector>
#include <algorithm>
#include <random>
using namespace std;

#ifdef __cplusplus
extern "C" {
#endif

	int get_n();
	int is_clockwise(int a, int b, int c);
	void give_answer(int s);

#ifdef __cplusplus
}
#endif

mt19937 ggg;

long long ccin_n() {
	return get_n();
	/*long long zzz;
	cin >> zzz;
	return zzz;*/
}

vector<long long> reall;

bool aski(long long a, long long b, long long c) {
	return is_clockwise(reall[a] + 1, reall[b] + 1, reall[c] + 1);
	/*cout << "? " << a << " " << b << " " << c << '\n';
	bool okak;
	cin >> okak;
	return okak;*/
}

bool cmpp(long long a, long long b) {
	if (a == 0) {
		return true;
	}
	if (a == 1) {
		return a < b;
	}
	if (b == 0) {
		return false;
	}
	if (b == 1) {
		return a < b;
	}
	bool aska = aski(1, 0, a);
	bool askb = aski(1, 0, b);
	if (aska && !askb) {
		return true;
	}
	if (!aska && askb) {
		return false;
	}
	return aski(a, 0, b);
}

void say_anse(long long x) {
	give_answer(x);
	//cout << "! " << x;
}

int main() {
	long long n = ccin_n();
	vector<long long> srt(n);
	for (long long i = 0; i < n; i++) {
		srt[i] = i;
	}
	reall = srt;
	shuffle(reall.begin(), reall.end(), ggg);
	sort(srt.begin(), srt.end(), cmpp);
	long long ii = -1;
	for (long long i = 1; i + 1 < n; i++) {
		if (aski(0, srt[i], srt[i + 1])) {
			ii = i + 1;
			break;
		}
	}
	if (ii == -1) {
		vector<long long> ch;
		for (auto i : srt) {
			if (ch.size() < 2) {
				ch.push_back(i);
				continue;
			}
			while (ch.size() >= 2 && aski(ch[ch.size() - 2], ch.back(), i)) {
				ch.pop_back();
			}
			ch.push_back(i);
		}
		vector<long long> sv = ch;
		vector<bool> delet(n);
		for (auto i : srt) {
			if (ch.size() < 2) {
				ch.push_back(i);
				continue;
			}
			while (ch.size() >= 2 && aski(ch[ch.size() - 2], ch.back(), i)) {
				delet[ch.back()] = 1;
				ch.pop_back();
			}
			ch.push_back(i);
		}
		long long ans = sv.size();
		for (auto x : sv) {
			if (delet[x]) {
				ans--;
			}
		}
		say_anse(ans);
	}
	else {
		vector<long long> newsrt = { 0 };
		for (long long j = ii; j < n; j++) {
			newsrt.push_back(srt[j]);
		}
		for (long long j = 1; j < ii; j++) {
			newsrt.push_back(srt[j]);
		}
		//cout << ii << " " << srt[ii] << '\n';
		srt = newsrt;
		/*for (auto gh : srt) {
			cout << gh << " ";
		}
		cout << '\n';*/
		vector<long long> ch;
		for (auto i : srt) {
			if (ch.size() < 2) {
				ch.push_back(i);
				continue;
			}
			while (ch.size() >= 2 && aski(ch[ch.size() - 2], ch.back(), i)) {
				ch.pop_back();
			}
			ch.push_back(i);
		}
		/*for (auto gh : ch) {
			cout << gh << " ";
		}
		cout << '\n';*/
		say_anse(ch.size());
	}
}

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