test/AOJ/CGL_4_A.test.cpp

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• Last update: 2024-08-24 11:50:18+09:00
• Problem: https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=CGL_4_A

Depends on

• 凸包 (geomeny/convex-hull.hpp)
• 幾何テンプレート (geomeny/geomeny-template.hpp)
• template/alias.hpp
• template/debug.hpp
• template/func.hpp
• template/macro.hpp
• template/template.hpp
• template/util.hpp

Code

#define PROBLEM \
    "https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=CGL_4_A"
#include "../../geomeny/convex-hull.hpp"
#include "../../template/template.hpp"

int main() {
    int N;
    cin >> N;
    vector<Point> A(N);
    for (int i = 0; i < N; ++i) {
        cin >> A[i].x >> A[i].y;
    }
    auto pol = ConvexHullCollinearOK(A);
    pair<ld, ld> minv = {11000, 11000};
    int minp = -1;
    for (int i = 0; i < (int)pol.size(); ++i) {
        if (minv > make_pair(pol[i].y, pol[i].x)) {
            minv = make_pair(pol[i].y, pol[i].x);
            minp = i;
        }
    }
    cout << pol.size() << endl;
    for (int i = 0; i < (int)pol.size(); ++i) {
        int j = (i + minp) % pol.size();
        cout << fixed << setprecision(0) << pol[j].x << " " << pol[j].y << endl;
    }
}

#line 1 "test/AOJ/CGL_4_A.test.cpp"
#define PROBLEM \
    "https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=CGL_4_A"
#line 2 "template/template.hpp"
#include <bits/stdc++.h>
#line 3 "template/macro.hpp"

#define overload3(_1, _2, _3, name, ...) name
#define all1(v) std::begin(v), std::end(v)
#define all2(v, a) std::begin(v), std::begin(v) + a
#define all3(v, a, b) std::begin(v) + a, std::begin(v) + b
#define all(...) overload3(__VA_ARGS__, all3, all2, all1)(__VA_ARGS__)
#define rall1(v) std::rbegin(v), std::rend(v)
#define rall2(v, a) std::rbegin(v), std::rbegin(v) + a
#define rall3(v, a, b) std::rbegin(v) + a, std::rbegin(v) + b
#define rall(...) overload3(__VA_ARGS__, rall3, rall2, rall1)(__VA_ARGS__)
#define elif else if
#define updiv(N, X) (((N) + (X) - 1) / (X))
#define sigma(a, b) (((a) + (b)) * ((b) - (a) + 1) / 2)
#define INT(...)     \
    int __VA_ARGS__; \
    scan(__VA_ARGS__)
#define LL(...)     \
    ll __VA_ARGS__; \
    scan(__VA_ARGS__)
#define STR(...)        \
    string __VA_ARGS__; \
    scan(__VA_ARGS__)
#define CHR(...)      \
    char __VA_ARGS__; \
    scan(__VA_ARGS__)
#define DOU(...)        \
    double __VA_ARGS__; \
    scan(__VA_ARGS__)
#define LD(...)     \
    ld __VA_ARGS__; \
    scan(__VA_ARGS__)
#define pb push_back
#define eb emplace_back
#line 3 "template/alias.hpp"

using ll = long long;
using ld = long double;
using pii = std::pair<int, int>;
using pll = std::pair<ll, ll>;
constexpr int inf = 1 << 30;
constexpr ll INF = 1LL << 60;
constexpr int dx[8] = {1, 0, -1, 0, 1, -1, 1, -1};
constexpr int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
constexpr int mod = 998244353;
constexpr int MOD = 1e9 + 7;
#line 3 "template/func.hpp"

template <typename T>
inline bool chmax(T& a, T b) { return ((a < b) ? (a = b, true) : (false)); }
template <typename T>
inline bool chmin(T& a, T b) { return ((a > b) ? (a = b, true) : (false)); }
template <typename T, typename U>
std::ostream &operator<<(std::ostream &os, const std::pair<T, U> &p) {
    os << p.first << " " << p.second;
    return os;
}
template <typename T, typename U>
std::istream &operator>>(std::istream &is, std::pair<T, U> &p) {
    is >> p.first >> p.second;
    return is;
}
template <typename T>
std::ostream &operator<<(std::ostream &os, const std::vector<T> &v) {
    for (auto it = std::begin(v); it != std::end(v);) {
        os << *it << ((++it) != std::end(v) ? " " : "");
    }
    return os;
}
template <typename T>
std::istream &operator>>(std::istream &is, std::vector<T> &v) {
    for (T &in : v) {
        is >> in;
    }
    return is;
}
inline void scan() {}
template <class Head, class... Tail>
inline void scan(Head &head, Tail &...tail) {
    std::cin >> head;
    scan(tail...);
}
template <class T>
inline void print(const T &t) { std::cout << t << '\n'; }
template <class Head, class... Tail>
inline void print(const Head &head, const Tail &...tail) {
    std::cout << head << ' ';
    print(tail...);
}
template <class... T>
inline void fin(const T &...a) {
    print(a...);
    exit(0);
}
#line 3 "template/util.hpp"

struct IOSetup {
    IOSetup() {
        std::cin.tie(nullptr);
        std::ios::sync_with_stdio(false);
        std::cout.tie(0);
        std::cout << std::fixed << std::setprecision(12);
        std::cerr << std::fixed << std::setprecision(12);
    }
} IOSetup;
#line 3 "template/debug.hpp"

#ifdef LOCAL
#include <dump.hpp>
#else
#define debug(...)
#endif
#line 8 "template/template.hpp"
using namespace std;
#line 3 "geomeny/geomeny-template.hpp"

using DD = long double;
const DD EPS = 1e-10;
const DD PI = acosl(-1.0);
DD torad(int deg) { return (DD)(deg)*PI / 180; }
DD todeg(DD ang) { return ang * 180 / PI; }

/* Point */
struct Point {
    DD x, y;
    Point(DD x = 0.0, DD y = 0.0) : x(x), y(y) {}
    friend ostream &operator<<(ostream &s, const Point &p) { return s << '(' << p.x << ", " << p.y << ')'; }
};
inline Point operator+(const Point &p, const Point &q) { return Point(p.x + q.x, p.y + q.y); }
inline Point operator-(const Point &p, const Point &q) { return Point(p.x - q.x, p.y - q.y); }
inline Point operator*(const Point &p, DD a) { return Point(p.x * a, p.y * a); }
inline Point operator*(DD a, const Point &p) { return Point(a * p.x, a * p.y); }
inline Point operator*(const Point &p, const Point &q) { return Point(p.x * q.x - p.y * q.y, p.x * q.y + p.y * q.x); }
inline Point operator/(const Point &p, DD a) { return Point(p.x / a, p.y / a); }
inline Point conj(const Point &p) { return Point(p.x, -p.y); }
inline Point rot(const Point &p, DD ang) { return Point(cos(ang) * p.x - sin(ang) * p.y, sin(ang) * p.x + cos(ang) * p.y); }
inline Point rot90(const Point &p) { return Point(-p.y, p.x); }
inline DD cross(const Point &p, const Point &q) { return p.x * q.y - p.y * q.x; }
inline DD dot(const Point &p, const Point &q) { return p.x * q.x + p.y * q.y; }
inline DD norm(const Point &p) { return dot(p, p); }
inline DD abs(const Point &p) { return sqrt(dot(p, p)); }
inline DD amp(const Point &p) {
    DD res = atan2(p.y, p.x);
    if (res < 0) res += PI * 2;
    return res;
}
inline bool eq(const Point &p, const Point &q) { return abs(p - q) < EPS; }
inline bool operator<(const Point &p, const Point &q) { return (abs(p.x - q.x) > EPS ? p.x < q.x : p.y < q.y); }
inline bool operator>(const Point &p, const Point &q) { return (abs(p.x - q.x) > EPS ? p.x > q.x : p.y > q.y); }
inline Point operator/(const Point &p, const Point &q) { return p * conj(q) / norm(q); }

/* Line */
struct Line : vector<Point> {
    Line(Point a = Point(0.0, 0.0), Point b = Point(0.0, 0.0)) {
        this->push_back(a);
        this->push_back(b);
    }
    friend ostream &operator<<(ostream &s, const Line &l) { return s << '{' << l[0] << ", " << l[1] << '}'; }
};

/* Circle */
struct Circle : Point {
    DD r;
    Circle(const Point &p = Point(0.0, 0.0), DD r = 0.0) : Point(p), r(r) {}
    friend ostream &operator<<(ostream &s, const Circle &c) { return s << '(' << c.x << ", " << c.y << ", " << c.r << ')'; }
};
#line 4 "geomeny/convex-hull.hpp"

vector<Point> ConvexHull(vector<Point> &ps) {
    int n = (int)ps.size();
    vector<Point> res(2 * n);
    sort(ps.begin(), ps.end());
    int k = 0;
    for (int i = 0; i < n; ++i) {
        if (k >= 2) {
            while (cross(res[k - 1] - res[k - 2], ps[i] - res[k - 2]) < EPS) {
                --k;
                if (k < 2) break;
            }
        }
        res[k] = ps[i];
        ++k;
    }
    int t = k + 1;
    for (int i = n - 2; i >= 0; --i) {
        if (k >= t) {
            while (cross(res[k - 1] - res[k - 2], ps[i] - res[k - 2]) < EPS) {
                --k;
                if (k < t) break;
            }
        }
        res[k] = ps[i];
        ++k;
    }
    res.resize(k - 1);
    return res;
}

vector<Point> ConvexHullCollinearOK(vector<Point> &ps) {
    int n = (int)ps.size();
    vector<Point> res(2 * n);
    sort(ps.begin(), ps.end());
    int k = 0;
    for (int i = 0; i < n; ++i) {
        if (k >= 2) {
            while (cross(res[k - 1] - res[k - 2], ps[i] - res[k - 2]) < -EPS) {
                --k;
                if (k < 2) break;
            }
        }
        res[k] = ps[i];
        ++k;
    }
    int t = k + 1;
    for (int i = n - 2; i >= 0; --i) {
        if (k >= t) {
            while (cross(res[k - 1] - res[k - 2], ps[i] - res[k - 2]) < -EPS) {
                --k;
                if (k < t) break;
            }
        }
        res[k] = ps[i];
        ++k;
    }
    res.resize(k - 1);
    return res;
}
#line 5 "test/AOJ/CGL_4_A.test.cpp"

int main() {
    int N;
    cin >> N;
    vector<Point> A(N);
    for (int i = 0; i < N; ++i) {
        cin >> A[i].x >> A[i].y;
    }
    auto pol = ConvexHullCollinearOK(A);
    pair<ld, ld> minv = {11000, 11000};
    int minp = -1;
    for (int i = 0; i < (int)pol.size(); ++i) {
        if (minv > make_pair(pol[i].y, pol[i].x)) {
            minv = make_pair(pol[i].y, pol[i].x);
            minp = i;
        }
    }
    cout << pol.size() << endl;
    for (int i = 0; i < (int)pol.size(); ++i) {
        int j = (i + minp) % pol.size();
        cout << fixed << setprecision(0) << pol[j].x << " " << pol[j].y << endl;
    }
}

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