Submission #918181

#	Time	Username	Problem	Language	Result	Execution time	Memory
918181		NK_	Triangles (CEOI18_tri)	C++17	100 / 100	24 ms	3484 KiB

tri

// Success consists of going from failure to failure without loss of enthusiasm
#include <bits/stdc++.h>
#include "trilib.h"
 
using namespace std;
 
#define nl '\n'
#define pb push_back
#define sz(x) int(x.size())
 
template<class T> using V = vector<T>;
using vi = V<int>;
 
mt19937 rng(1008);
 
// g++-13 -O2 trilib.cpp A.cpp -std=c++17 -o ./G
int main() {
	cin.tie(0)->sync_with_stdio(0);
	int N = get_n();
 
	function<vi(vi)> dnc = [&](vi A) {
		if (sz(A) <= 1) return A;
 
		int M = A[rng() % sz(A)]; vi L, R;
 
		for(auto& x : A) if (x != M) {
			if (!is_clockwise(1, M + 1, x + 1)) L.pb(x);
			else R.pb(x);
		}
 
		L = dnc(L); R = dnc(R);
 
		L.pb(M);
		L.insert(end(L), begin(R), end(R));
 
		return L;
	};
 
	vi A(N - 1); iota(begin(A), end(A), 1);
 
	A = dnc(A); A.insert(begin(A), 0);
 
	// for(auto& x : A) cout << x << " ";
	// cout << endl;
 
	auto fix = [&](vi A) {
		vi C = {A[0]};
		for(int i = 1; i < sz(A); i++) {
			while(sz(C) >= 2 && !is_clockwise(C[sz(C) - 2] + 1, C[sz(C) - 1] + 1, A[i] + 1)) C.pop_back();
			C.pb(A[i]);
		}
 
		return C;
	};

	// for(auto& x : C) cout << x << " ";
 	// cout << endl;
	A = fix(A);
	deque<int> D(begin(A), end(A));

	while(1) {
			
		bool done = 1;

		int x = D.back(); D.pop_back();
		if (!is_clockwise(D.back() + 1, x + 1, D.front() + 1)) done = 0;
		else D.pb(x);

		int y = D.front(); D.pop_front();
		if (!is_clockwise(D.back() + 1, y + 1, D.front() + 1)) done = 0;
		else D.push_front(y);

		if (done) break;
	}

	// for(auto& x : D) cout << x << " ";
	// cout << endl;
 
	give_answer(sz(D));
 
	exit(0-0);
}

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