Submission #1229396

#	Time	Username	Problem	Language	Result	Execution time	Memory
1229396		radodododo	Triangles (CEOI18_tri)	C++20	0 / 100	0 ms	328 KiB

tri

#include <iostream>
#include <vector>
#include <algorithm>
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

long long ccin_n() {
	return get_n();
}

bool aski(long long a, long long b, long long c) {
	return is_clockwise(a + 1, b + 1, c + 1);
}

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);
}

int main() {
	long long n = ccin_n();
	vector<long long> srt(n);
	for (long long i = 0; i < n; i++) {
		srt[i] = i;
	}
	sort(srt.begin(), srt.end(), cmpp);
	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);
}

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