Submission #898146

#	Time	Username	Problem	Language	Result	Execution time	Memory
898146		alexdd	Triangles (CEOI18_tri)	C++17	0 / 100	1 ms	348 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) && (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;
    }
    centru=3;
    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]))
            hull.push_back(ord[i]);
        else
        {

        }
    }
    int idk=1, siz=hull.size();
    for(int i=0;i<hull.size();i++)
    {
        if(is_inter(centru,hull[i],hull[(i+1)%siz],hull[(i+2)%siz]))
        {
            idk=0;
            break;
        }
    }
    give_answer(max(3,(int)hull.size() + idk));
}

Compilation message (stderr)

tri.cpp: In function 'bool is_inter(int, int, int, int)':
tri.cpp:13:32: warning: left operand of comma operator has no effect [-Wunused-value]
   13 |     if(is_clockwise(a,b,c) && (x,b,c) && is_clockwise(x,a,b) && is_clockwise(x,c,a))
      |                                ^
tri.cpp:13:36: warning: right operand of comma operator has no effect [-Wunused-value]
   13 |     if(is_clockwise(a,b,c) && (x,b,c) && is_clockwise(x,a,b) && is_clockwise(x,c,a))
      |                                    ^
tri.cpp: In function 'int main()':
tri.cpp:34:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   34 |     for(int i=2;i<ord.size();i++)
      |                 ~^~~~~~~~~~~
tri.cpp:46:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   46 |     for(int i=0;i<hull.size();i++)
      |                 ~^~~~~~~~~~~~

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