Submission #1280052

#	Time	Username	Problem	Language	Result	Execution time	Memory
1280052		knhatdev	Planine (COCI21_planine)	C++20	110 / 110	162 ms	23932 KiB

Main

#include<bits/stdc++.h>
#define int long long
#define ii pair<int,int>
#define dd pair<double, double>
#define fi first
#define se second
#define task ""
using namespace std;

const int N = 1e6 + 5, oo = 1e18;

#define EPS  0.00001
struct point2d{
    int x, y;
    point2d() {}
    point2d(int x, int y): x(x), y(y) {}

    point2d operator + (point2d t){
        return point2d(x + t.x, y + t.y);
    }
    point2d operator - (point2d t){
        return point2d(x - t.x, y - t.y);
    }
};
struct point{
    double x, y;
    point() {}
    point(int x, int y): x(x), y(y) {}

    point operator + (point t){
        return point(x + t.x, y + t.y);
    }
    point operator - (point t){
        return point(x - t.x, y - t.y);
    }
};
struct line2d{
    int a, b, c;
    line2d(int a, int b, int c): a(a), b(b), c(c) {}
    line2d(point2d &u, point2d &v) :  a(u.y - v.y), b(v.x - u.x), c(u.x * v.y - v.x * u.y) {};
};

int cross(point2d a, point2d b){ //tich co huong
    return a.x * b.y - a.y * b.x;
}
int dot(point2d a, point2d b){ // tich vo huong
    return a.x * b.x + a.y * b.y;
}
double abs(point2d a) {
    return sqrt(a.x * a.x + a.y * a.y);
}
double angle(point2d a, point2d b){ // goc giua 2 vector
    return acos(dot(a, b) / abs(a) / abs(b));
}
point get_intersect(line2d x, line2d y) {
    int d = x.a * y.b - x.b * y.a;
    if(d == 0) return {oo, oo};
    //Neu d == 0: 2 duong song song hoac trung nhau
    point t;
    t.x = (double)(x.b * y.c - y.b * x.c) / d;
    t.y = (double)(y.a * x.c - x.a * y.c) / d;
    return t;
}

int ccw(point2d a, point2d b, point2d c) {
    int t = cross(b - a, c - b);
    if (t == 0) return 0;
    if (t < 0) return -1;
        else return 1;
}

int n;
int h;
point2d a[N];
dd b[N];

main(){
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    if(fopen(task ".inp", "r")){
        freopen(task ".inp", "r", stdin);
        freopen(task ".out", "w", stdout);
    }
    cin >> n >> h;
    for(int i = 1; i <= n; i++)
    {
        cin >> a[i].x >> a[i].y;
    }
    line2d tmp(0, 1, -h);
    int m = 0;
    vector<int> v;
    v.push_back(1);
    v.push_back(2);
    for(int i = 3; i < n; i++)
    {
        while(v.size() >= 2 && ccw(a[v[v.size() - 2]], a[v[v.size() - 1]], a[i]) >= 0)
        {
            v.pop_back();
        }

        v.push_back(i);
        // for(int x : v) cout << x << ' ';
        // cout << '\n';
        if(i % 2 == 1)
        {
            // cout << a[i].x << ' ' << a[i].y << "; " << a[v[v.size() - 2]].x << ' ' << a[v[v.size() - 2]].y << '\n';
            point x = get_intersect(line2d(a[i], a[v[v.size() - 2]]), tmp);
            b[++m].fi = x.x;
        }
        // cout << b[m].fi << ' ' << b[m].se << '\n';
    }
    int j = m;
    v.clear();
    v.push_back(n);
    v.push_back(n - 1);
    for(int i = n - 2; i >= 3; i--)
    {
        while(v.size() >= 2 && ccw(a[v[v.size() - 2]], a[v[v.size() - 1]], a[i]) <= 0)
        {
            v.pop_back();
        }
        v.push_back(i);
        if(i % 2 == 1)
        {
            point x = get_intersect(line2d(a[i], a[v[v.size() - 2]]), tmp);
            b[j--].se = x.x;
        }
    }
    // for(int i = 1; i <= m; i++)
    //     cout << b[i].fi << ' ' << b[i].se << '\n';

    sort(b + 1, b + 1 + m, [](dd x, dd y)
    {
        return (x.se < y.se) || (x.se == y.se && x.fi < y.fi);
    });
    double last_pos = -1e18;
    int ans = 0;
    for(int i = 1; i <= m; i++)
    {
        if(b[i].fi - EPS > last_pos)
        {
            ans++;
            last_pos = b[i].se;
        }
    }
    cout << ans;
}

Compilation message (stderr)

Main.cpp:77:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   77 | main(){
      | ^~~~
Main.cpp: In function 'int main()':
Main.cpp:80:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   80 |         freopen(task ".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:81:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   81 |         freopen(task ".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

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