Submission #305129

#	Time	Username	Problem	Language	Result	Execution time	Memory
305129		miss_robot	Triangles (CEOI18_tri)	C++14	100 / 100	540 ms	58984 KiB

tri

#include "trilib.h"
#include <bits/stdc++.h>

#pragma GCC optimize("O3")

using namespace std;

map<tuple<int, int, int>, int> q;

int qry(int a, int b, int c){
	int d = a, e = b, f = c;
	if(f < d) swap(d, f);
	if(e < d) swap(d, e);
	if(e < f) swap(e, f);
	int dir;
	if(a == d) dir = (b == e);
	else if(a == e) dir = (b == f);
	else dir = (b == d);
	if(q.count({d, e, f})){
		if(dir) return q[{d, e, f}];
		return q[{d, e, f}]^1;
	}
	int r = is_clockwise(a, b, c);
	if(dir) q[{d, e, f}] = r;
	else q[{d, e, f}] = r^1;
	return r;
}

void qsort(deque<int>& p, deque<int>& t){
	if(t.size() == 0) return;
	if(t.size() == 1){
		p.push_back(t[0]);
		return;
	}
	int x = rand()%t.size();
	deque<int> left, right;
	for(int i = 0; i < (int)t.size(); i++){
		if(i == x) continue;
		if(qry(1, t[x], t[i])) right.push_back(t[i]);
		else left.push_back(t[i]);
	}
	qsort(p, left);
	p.push_back(t[x]);
	qsort(p, right);
}

int main(){
	srand(time(0));
	cin.tie(0);
	ios::sync_with_stdio(0);
	int n = get_n();
	deque<int> p, t, h(n+1);
	for(int i = 2; i <= n; i++) t.push_back(i);
	qsort(p, t);
	int s = 2;
	h[0] = 1, h[1] = p[0];
	for(int i = 1; i < n-1; i++){
		while(s > 1 && !qry(h[s-2], h[s-1], p[i])) s--;
		h[s++] = p[i];
	}
	int cng = 1;
	while(cng){
		cng = 0;
		while(s > 2 && !qry(h[s-2], h[s-1], h[0])){
			s--;
			cng = 1;
		}
		while(s > 2 && !qry(h[s-1], h[0], h[1])){
			s--;
			h.pop_front();
			cng = 1;
		}
		while(s > 2 && !qry(h[0], h[1], h[2])){
			s--;
			int temp = h.front();
			h.pop_front(), h.pop_front();
			h.push_front(temp);
			cng = 1;
		}
	}
	give_answer(s);
}

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