Submission #1215965

#	Time	Username	Problem	Language	Result	Execution time	Memory
1215965		newsboy	Mobile (BOI12_mobile)	C++20	0 / 100	222 ms	40632 KiB

mobile

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <iomanip>
#include <set>
#include <map>
#include <numeric>
#include <iomanip>
#include <unordered_set>
#include <unordered_map>
#include <bitset>
#include <queue>
#include <deque>
#include <stack>
#include <cmath>
#include <tuple>
#include <cassert>
#include <array>
#include <list>
#include <random>
#include <initializer_list>
using namespace std;
using i64 = long long;
using u64 = unsigned long long;
using db = double;
using ld = long double;
constexpr i64 INF = 1E18;
constexpr i64 MIN = -INF;
constexpr i64 MAX = INF;
constexpr int N = 1E4 + 10;

struct Point {
    db x, y;
};

db dist(Point& a, Point& b) {
    db dx = abs(a.x - b.x), dy = abs(a.y - b.y);
    return sqrt(dx * dx + dy * dy);
}

db calc(Point& a, Point& b) {
    return (b.x * b.x + b.y * b.y - a.x * a.x - a.y * a.y) / (2 * (b.x - a.x));
}

void solve() {
    int n;
    db L;
    cin >> n >> L;
    vector<Point> points;
    for (int i = 0; i < n; ++i) {
        db x, y;
        cin >> x >> y;
        y = abs(y);
        while (!points.empty() && (points.back().x == x && points[i].y > y)) {
            points.pop_back();
        }
        if (points.empty() || points.back().x != x) {
            points.push_back({ x, y });
        }
    }
    vector<Point> t;
    for (int i = 0; i < points.size(); ++i) {
        while (t.size() > 1 && calc(t[t.size() - 2], t[t.size() - 1]) >= calc(t[t.size() - 1], points[i])) {
            t.pop_back();
        }
        t.push_back(points[i]);
    }
    reverse(t.begin(), t.end());
    while (t.size() > 1 && calc(t[t.size() - 2], t[t.size() - 1]) <= 0) {
        t.pop_back();
    }
    reverse(t.begin(), t.end());
    while (t.size() > 1 && calc(t[t.size() - 2], t[t.size() - 1]) >= L) {
        t.pop_back();
    }
    points = t;
    Point A = { 0, 0 };
    Point B = { L, 0 };
    db ans = max(dist(A, points[0]), dist(B, points.back()));
    for (int i = 1; i < points.size(); ++i) {
        Point tmp = { calc(points[i - 1], points[i]), 0 };
        ans = max(ans, dist(points[i], tmp));
    }
    cout << ans << '\n';
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout << fixed << setprecision(10);
    int t = 1;
    /*cin >> t;*/
    while (t--) {
        solve();
    }
    return 0;
}

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• Subtask 21: 0 / 5