Submission #503687

#	Time	Username	Problem	Language	Result	Execution time	Memory
503687		andrei_boaca	Triangles (CEOI18_tri)	C++17	15 / 100	1 ms	332 KiB

tri

#include <bits/stdc++.h>
#include "trilib.h"
//#include "trilib.c"
using namespace std;
mt19937 rng(time(NULL));
map<vector<int>,bool> f;
set<int> border;
vector<int> stiva,v;
int root;
bool use[40005];
int calls=0;
bool notgood[40005];
bool isgood(int a,int b,int c)
{
    vector<int> v;
    v.push_back(a);
    v.push_back(b);
    v.push_back(c);
    sort(v.begin(),v.end());
    if(f.count(v)==0)
    {
        f[v]=is_clockwise(v[0],v[1],v[2]);
        calls++;
        assert(calls<=1e6);
    }
    bool ans=f[v];
    int nr=0;
    if(a!=v[0])
        nr++;
    if(b!=v[1])
        nr++;
    if(c!=v[2])
        nr++;
    if(nr%2==0&&nr>0)
        ans=!ans;
    return ans;
}
bool comp(int a, int b)
{
    if(isgood(root,a,b))
        return 1;
    return 0;
}
set<int> ok;
int main()
{
    int n;
    n=get_n();
    int i=1;
    for(int i=1;i<=n;i++)
        ok.insert(i);
    while(border.empty())
        {
            int good=2;
            int val=-1;
            use[i]=1;
            ok.erase(i);
            if(ok.size()==3)
            {
                give_answer(3);
                return 0;
            }
            int j=1;
            for(j=1;j<=n;j++)
                if(notgood[j]==0&&i!=j)
                    break;
            bool need=1;
            for(int k=1;k<=n;k++)
                if(k!=i&&k!=j&&notgood[k]==0)
                    if(isgood(i,j,k)==need)
                        j=k;
            for(int k=1;k<=n;k++)
                if(k!=i&&k!=j&&notgood[k]==0)
                    if(isgood(i,j,k)==need)
                        good=0;
            if(good)
            {
                border.insert(i);
                border.insert(j);
                break;
            }
            else
            {
                notgood[i]=1;
                i=j;
                if(use[i])
                    i=*prev(ok.end());
            }
        }
    int j=*border.begin();
    stiva.push_back(j);
    root=j;
    for(int i=1;i<=n;i++)
        if(i!=j)
            v.push_back(i);
    sort(v.begin(),v.end(),comp);
    stiva.push_back(v[0]);
    for(int i=1;i<v.size();i++)
    {
        int nod=v[i];
        while(stiva.size()>=2)
        {
            int lg=stiva.size();
            int b=stiva[lg-1];
            int a=stiva[lg-2];
            if(!isgood(a,b,nod))
                stiva.pop_back();
            else
                break;
        }
        stiva.push_back(nod);
    }
    int ans=stiva.size();
    give_answer(ans);
    return 0;
}

Compilation message (stderr)

tri.cpp: In function 'int main()':
tri.cpp:55:17: warning: unused variable 'val' [-Wunused-variable]
   55 |             int val=-1;
      |                 ^~~
tri.cpp:98:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   98 |     for(int i=1;i<v.size();i++)
      |                 ~^~~~~~~~~

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