結果

問題 No.2012 Largest Triangle
ユーザー tokusakurai
提出日時 2022-07-16 17:35:16
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 119 ms / 2,500 ms
コード長 5,168 bytes
コンパイル時間 2,610 ms
コンパイル使用メモリ 207,216 KB
最終ジャッジ日時 2025-01-30 09:36:01
ジャッジサーバーID
（参考情報） 		judge3 / judge4
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 1
other AC * 41
権限があれば一括ダウンロードができます

ソースコード

diff # 

#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < n; i++)
#define rep2(i, x, n) for (int i = x; i <= n; i++)
#define rep3(i, x, n) for (int i = x; i >= n; i--)
#define each(e, v) for (auto &e : v)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;

template <typename T>
bool chmax(T &x, const T &y) {
    return (x < y) ? (x = y, true) : false;
}

template <typename T>
bool chmin(T &x, const T &y) {
    return (x > y) ? (x = y, true) : false;
}

template <typename T>
int flg(T x, int i) {
    return (x >> i) & 1;
}

template <typename T>
void print(const vector<T> &v, T x = 0) {
    int n = v.size();
    for (int i = 0; i < n; i++) cout << v[i] + x << (i == n - 1 ? '\n' : ' ');
    if (v.empty()) cout << '\n';
}

template <typename T>
void printn(const vector<T> &v, T x = 0) {
    int n = v.size();
    for (int i = 0; i < n; i++) cout << v[i] + x << '\n';
}

template <typename T>
int lb(const vector<T> &v, T x) {
    return lower_bound(begin(v), end(v), x) - begin(v);
}

template <typename T>
int ub(const vector<T> &v, T x) {
    return upper_bound(begin(v), end(v), x) - begin(v);
}

template <typename T>
void rearrange(vector<T> &v) {
    sort(begin(v), end(v));
    v.erase(unique(begin(v), end(v)), end(v));
}

template <typename T>
vector<int> id_sort(const vector<T> &v, bool greater = false) {
    int n = v.size();
    vector<int> ret(n);
    iota(begin(ret), end(ret), 0);
    sort(begin(ret), end(ret), [&](int i, int j) { return greater ? v[i] > v[j] : v[i] < v[j]; });
    return ret;
}

template <typename S, typename T>
pair<S, T> operator+(const pair<S, T> &p, const pair<S, T> &q) {
    return make_pair(p.first + q.first, p.second + q.second);
}

template <typename S, typename T>
pair<S, T> operator-(const pair<S, T> &p, const pair<S, T> &q) {
    return make_pair(p.first - q.first, p.second - q.second);
}

template <typename S, typename T>
istream &operator>>(istream &is, pair<S, T> &p) {
    S a;
    T b;
    is >> a >> b;
    p = make_pair(a, b);
    return is;
}

template <typename S, typename T>
ostream &operator<<(ostream &os, const pair<S, T> &p) {
    return os << p.first << ' ' << p.second;
}

struct io_setup {
    io_setup() {
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        cout << fixed << setprecision(15);
    }
} io_setup;

const int inf = (1 << 30) - 1;
const ll INF = (1LL << 60) - 1;
const int MOD = 1000000007;
// const int MOD = 998244353;

template <typename T>
vector<pair<T, T>> convex_hull_integer(vector<pair<T, T>> p) {
    sort(begin(p), end(p));
    p.erase(unique(begin(p), end(p)), end(p));
    int n = p.size(), k = 0;
    if (n == 1) return p;
    vector<pair<T, T>> ch(2 * n);
    for (int i = 0; i < n; ch[k++] = p[i++]) {
        while (k >= 2) {
            T x1 = ch[k - 1].first - ch[k - 2].first, y1 = ch[k - 1].second - ch[k - 2].second;
            T x2 = p[i].first - ch[k - 1].first, y2 = p[i].second - ch[k - 1].second;
            if (x1 * y2 - x2 * y1 <= 0) {
                k--;
            } else {
                break;
            }
        }
    }
    for (int i = n - 2, t = k + 1; i >= 0; ch[k++] = p[i--]) {
        while (k >= t) {
            T x1 = ch[k - 1].first - ch[k - 2].first, y1 = ch[k - 1].second - ch[k - 2].second;
            T x2 = p[i].first - ch[k - 1].first, y2 = p[i].second - ch[k - 1].second;
            if (x1 * y2 - x2 * y1 <= 0) {
                k--;
            } else {
                break;
            }
        }
    }
    ch.resize(k - 1);
    return ch;
}

template <typename T>
int type(pair<T, T> p) {
    if (p.first == 0 && p.second == 0) return 0;
    if (p.second < 0 || (p.second == 0 && p.first > 0)) return -1;
    return 1;
}

template <typename T>
bool compare_arg(pair<T, T> p, pair<T, T> q) {
    int a = type(p), b = type(q);
    if (a != b) return a < b;
    return p.first * q.second > q.first * p.second;
}

template <typename T>
void sort_arg(vector<pair<T, T>> &p) {
    sort(begin(p), end(p), compare_arg<T>);
}

int main() {
    int N;
    cin >> N;

    vector<pll> p(N);
    rep(i, N) cin >> p[i];

    auto q = convex_hull_integer(p);
    // each(e, q) cout << e << '\n';
    int K = sz(q);

    sort_arg(p);
    ll ans = 0;

    int ptr = 0;
    rep(i, K) {
        auto [x1, y1] = p[0];
        auto [x2, y2] = q[i];
        ll tmp = abs(x1 * y2 - x2 * y1);
        if (chmax(ans, tmp)) ptr = i;
    }

    rep2(i, 1, N - 1) {
        auto [x, y] = p[i];
        while (true) {
            auto [dx, dy] = q[(ptr + 1) % K] - q[ptr];
            if (x * dy - y * dx < 0) {
                ptr++, ptr %= K;
            } else {
                break;
            }
        }

        rep2(j, K - 1, K + 1) {
            int k = (ptr + j) % K;
            auto [x1, y1] = p[i];
            auto [x2, y2] = q[k];
            ll tmp = abs(x1 * y2 - x2 * y1);
            chmax(ans, tmp);
        }
    }

    cout << ans << '\n';
}
0