Submission #541384

#	Time	Username	Problem	Language	Result	Execution time	Memory
541384		AlperenT	Planine (COCI21_planine)	C++17	110 / 110	284 ms	77884 KiB

Main

#include <bits/stdc++.h>

using namespace std;

const int N = 1e6 + 5;

struct Point{
    long long x, y;
};

int n, ans;

Point arr[N];

long double l[N], r[N], h, mx;

vector<pair<long double, long double>> v;

int orient(Point a, Point b, Point c){
    long long diff = (c.y - b.y) * (b.x - a.x) - (b.y - a.y) * (c.x - b.x);

    if(diff < 0) return 1;
    else if(diff > 0) return -1;
    else return 0;
}

vector<Point> hull;

int main(){
    ios_base::sync_with_stdio(false);cin.tie(NULL);

    cin >> n >> h;

    for(int i = 1; i <= n; i++) cin >> arr[i].x >> arr[i].y;

    if(n == 3){
        cout << 0;
        return 0;
    }

    hull.push_back(arr[1]), hull.push_back(arr[2]);

    for(int i = 3; i <= n - 2; i += 2){
        while(hull.size() >= 2 && orient(hull[hull.size() - 2], hull[hull.size() - 1], arr[i]) != 1) hull.pop_back();

        l[i] = arr[i].x + ((h - arr[i].y) / (hull.back().y - arr[i].y)) * (hull.back().x - arr[i].x);

        hull.push_back(arr[i]);

        while(hull.size() >= 2 && orient(hull[hull.size() - 2], hull[hull.size() - 1], arr[i + 1]) != 1) hull.pop_back();

        hull.push_back(arr[i + 1]);
    }

    hull.clear();

    hull.push_back(arr[n]), hull.push_back(arr[n - 1]);

    for(int i = n - 2; i >= 3; i -= 2){
        while(hull.size() >= 2 && orient(hull[hull.size() - 2], hull[hull.size() - 1], arr[i]) != -1) hull.pop_back();

        r[i] = arr[i].x + ((h - arr[i].y) / (hull.back().y - arr[i].y)) * (hull.back().x - arr[i].x);

        hull.push_back(arr[i]);

        while(hull.size() >= 2 && orient(hull[hull.size() - 2], hull[hull.size() - 1], arr[i - 1]) != -1) hull.pop_back();

        hull.push_back(arr[i - 1]);
    }

    for(int i = 3; i <= n - 2; i += 2) v.push_back({r[i], l[i]});

    sort(v.begin(), v.end());

    mx = v[0].first, ans = 1;

    for(int i = 1; i < v.size(); i++){
        if(v[i].second <= mx) continue;
        else ans++, mx = v[i].first;
    }

    cout << ans;
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:77:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<long double, long double> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   77 |     for(int i = 1; i < v.size(); i++){
      |                    ~~^~~~~~~~~~

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