Submission #898329

#	Time	Username	Problem	Language	Result	Execution time	Memory
898329		alexdd	Triangles (CEOI18_tri)	C++17	35 / 100	3094 ms	600 KiB

tri

#include<bits/stdc++.h>
#include "trilib.h"
using namespace std;
int n,centru;
bool cmp(int x, int y)
{
    if(is_clockwise(centru,x,y))
        return 1;
    return 0;
}
bool is_inter(int x, int a, int b, int c)///is x in the triangle (a,b,c)
{
    if(!is_clockwise(a,b,c))
    {
        if(is_clockwise(x,b,a) && is_clockwise(x,c,b) && is_clockwise(x,a,c))
            return 1;
        else
            return 0;
    }
    else if(is_clockwise(x,b,c) && is_clockwise(x,a,b) && is_clockwise(x,c,a))
        return 1;
    return 0;
}
signed main()
{
    n = get_n();
    if(n==3)
    {
        give_answer(3);
        return 0;
    }
    if(n<=50)
    {
        int cnt=0;
        for(int i=1;i<=n;i++)
        {
            bool bun=1;
            int a=1;
            if(i==1)
                a=2;
            for(int b=a+1;b<=n;b++)
            {
                if(!bun) break;
                if(b==i)
                    continue;
                for(int c=b+1;c<=n;c++)
                {
                    if(!bun) break;
                    if(c==i)
                        continue;
                    if(is_inter(i,a,b,c))
                        bun=0;
                }
            }
            if(bun)
                cnt++;
        }
        give_answer(cnt);
        return 0;
    }
    centru=n/2;
    vector<int> ord;
    for(int i=1;i<=n;i++)
        if(i!=centru)
            ord.push_back(i);
    sort(ord.begin(),ord.end(),cmp);
    vector<int> hull;
    hull.push_back(ord[0]);
    hull.push_back(ord[1]);
    for(int i=2;i<ord.size();i++)
    {
        while((int)hull.size()>=2 && is_inter(hull.back(), centru, hull[(int)hull.size()-2], ord[i]))
            hull.pop_back();
        if(((int)hull.size()<2 || (!is_inter(ord[i], centru, hull.back(), hull[0]))) && ((int)hull.size()<3 || 1 || (!is_inter(ord[i],hull[(int)hull.size()-2],hull.back(),hull[0]) /*&& is_clockwise(hull[(int)hull.size()-2],hull.back(),hull[0])*/)))
            hull.push_back(ord[i]);
    }
    //if((int)hull.size()>=3 && !is_clockwise(hull.back(),hull[0],hull[1]))
      //  hull.erase(hull.begin());
    int idk=1;
    if((int)hull.size()>=3)
    {
        for(int i=0;i<hull.size();i++)
        {
            if(!is_clockwise(hull[i],hull[(i+1)%((int)hull.size())],hull[(i+2)%((int)hull.size())]))
            {
                while(1)
                    n=0;
            }
            if(is_inter(centru,hull[i],hull[(i+1)%((int)hull.size())],hull[(i+2)%((int)hull.size())]))
            {
                idk=0;
            }
        }
    }
    give_answer(max(3,(int)hull.size() + idk));
}

Compilation message (stderr)

tri.cpp: In function 'int main()':
tri.cpp:70:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   70 |     for(int i=2;i<ord.size();i++)
      |                 ~^~~~~~~~~~~
tri.cpp:82:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   82 |         for(int i=0;i<hull.size();i++)
      |                     ~^~~~~~~~~~~~

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