Submission #538117

#	Time	Username	Problem	Language	Result	Execution time	Memory
538117		siewjh	Planine (COCI21_planine)	C++17	30 / 110	140 ms	6012 KiB

Main

#include <bits/stdc++.h>
typedef long double ld;
using namespace std;
int nums, h;
struct pt{
    ld x, y;
};
struct hull{
    vector<pt> v;
    ld intersect(pt a, pt b){
        ld m = (b.y - a.y) / (b.x - a.x), c = b.y - b.x * m;
        return (h - c) / m;
    }
    void insert(pt p){
        while (!v.empty() && v.back().y <= p.y) v.pop_back();
        v.push_back(p);
    }
    ld query(pt p){
        while (v.size() >= 2 && abs(intersect(p, v.back()) - p.x) >= abs(intersect(p, v[v.size() - 2]) - p.x)) v.pop_back();
        return intersect(p, v.back());
    }
};
bool cmp(pair<int, int> a, pair<int, int> b){
    return a.second < b.second;
}
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    cin >> nums >> h;
    vector<pt> vec(nums);
    for (int i = 0; i < nums; i++) cin >> vec[i].x >> vec[i].y;
    int valley = (nums - 3) / 2;
    vector<pair<ld, ld>> range(valley);
    hull left;
    for (int i = 1, j = 0; i < nums - 1; i++){
        if (i % 2) left.insert(vec[i]);
        else {
            range[j].first = left.query(vec[i]);
            j++;
        }
    }
    hull right;
    for (int i = nums - 2, j = valley - 1; i >= 1; i--){
        if (i % 2) right.insert(vec[i]);
        else {
            range[j].second = right.query(vec[i]);
            j--;
        }
    }
    sort(range.begin(), range.end(), cmp);
    int ans = 0; ld last_pos = -1e18;
    for (int i = 0; i < valley; i++)
        if (range[i].first > last_pos){
            ans++;
            last_pos = range[i].second;
        }
    cout << ans;
}

• Subtask 1: 0 / 20
• Subtask 2: 30 / 30
• Subtask 3: 0 / 60