Submission #367292

#	Time	Username	Problem	Language	Result	Execution time	Memory
367292		MrRobot_28	Planine (COCI21_planine)	C++17	110 / 110	682 ms	88388 KiB

Main

#include<bits/stdc++.h>
using namespace std;
#define X first
#define Y second
#define int long long
int crossproduct(pair <int, int> a, pair <int, int> b, pair <int, int> c)
{
    return (b.X- a.X) * (c.Y - a.Y) - (b.Y - a.Y) * (c.X - a.X);
}
int n, h;
vector <pair <int, int> > funct(vector <pair <int, int> > x)
{
    vector <pair <int, int> > res(n / 2 - 1);
    vector <pair <int, int> > st;
    for(int i = 1; i < n - 1; i++)
    {
        while(st.size() > 1 && crossproduct(st[st.size() - 2], st.back(), x[i]) >= 0)
        {
            st.pop_back();
        }
        st.push_back(x[i]);
        if(!(i & 1))
        {
            auto [x1, y1] = st.rbegin()[0];
            auto [x2, y2] = st.rbegin()[1];
            /*int x1 = st[st.size() - 2].X;
            int y1 = st[st.size() - 2].Y;
            int x2 = x[i].X;
            int y2 = x[i].Y;*/
            int x0 = (x1 - x2) * (h - y2) + x2 * (y1 - y2);
            int y0 = y1 - y2;
          //  cout << st.size() << "\n";
            res[i / 2 - 1] = {x0, y1 - y2};
        }
    }
    return res;
}
bool cmp(pair <pair <int, int>, pair <int, int> > a, pair <pair <int, int>, pair <int, int> > b)
{
    if(a.X.X * b.X.Y == a.X.Y * b.X.X)
    {
        return a.Y.X < b.Y.X;
    }
    return a.X.X * b.X.Y < a.X.Y * b.X.X;
}
signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> h;
    vector <pair <int, int> > x(n);
    for(int i = 0; i < n; i++)
    {
        cin >> x[i].X >> x[i].Y;
    }
    vector <pair <int, int> > a = funct(x);
    reverse(x.begin(), x.end());
    for(int i = 0; i < n; i++)
    {
        x[i].X *= -1;
    }
    vector <pair <int, int> > b = funct(x);
    reverse(b.begin(), b.end());
    for(int i = 0; i < b.size(); i++)
    {
        b[i].X *= -1;
    }
    int ans = 0;
    vector <pair <pair <int, int>, pair <int, int> > > scan;
    for(int i = 0; i < n / 2 - 1; i++)
    {
        scan.push_back({a[i], {-1, i}});
        scan.push_back({b[i], {1, i}});
    }
    sort(scan.begin(), scan.end(), cmp);
    set <int> s;
    for(int i = 0; i < scan.size(); i++)
    {
        int t = scan[i].Y.X;
        if(t == -1)
        {
            s.insert(scan[i].Y.Y);
        }
        else if(s.find(scan[i].Y.Y) != s.end())
        {
            ans++;
            s.clear();
        }
    }
    cout << ans;
    return 0;
}

Compilation message (stderr)

Main.cpp: In function 'std::vector<std::pair<long long int, long long int> > funct(std::vector<std::pair<long long int, long long int> >)':
Main.cpp:31:17: warning: unused variable 'y0' [-Wunused-variable]
   31 |             int y0 = y1 - y2;
      |                 ^~
Main.cpp: In function 'int main()':
Main.cpp:65:22: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   65 |     for(int i = 0; i < b.size(); i++)
      |                    ~~^~~~~~~~~~
Main.cpp:78:22: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<std::pair<long long int, long long int>, std::pair<long long int, long long int> > >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   78 |     for(int i = 0; i < scan.size(); i++)
      |                    ~~^~~~~~~~~~~~~

• Subtask 1: 20 / 20
• Subtask 2: 30 / 30
• Subtask 3: 60 / 60