Отбор на Чемпионат юга 2018. Задача E

package net.egork;

import net.egork.io.IOUtils;
import net.egork.utils.io.InputReader;
import net.egork.utils.io.OutputWriter;

import java.util.Comparator;
import java.util.List;

public class TaskE {
    public void solve(int testNumber, InputReader in, OutputWriter out) {
        time = in.readInt();
        width = in.readInt();
        yRoad = in.readInt();
        carVelocity = in.readInt();

        columnStarts = IOUtils.readIntArray(in, columnCount = in.readInt());
        carStarts = IOUtils.readLongArray(in, carCount = in.readInt());

        Event[] all = new Event[columnCount * 2 + 2];
        for (int i = 0; i < columnCount; i++) {
            add(all, new Event(columnStarts[i], 0), i * 2);
            add(all, new Event(columnStarts[i] + width, 1), i * 2 + 1);
        }

        double answer = 0;
        for (int i = 0; i < carCount; i++) {
            answer += solve(all, carStarts[i]);
        }
        out.printFormat("%.20f", answer);
    }

    double solve(Event[] events, long carStart) {
        Event START_EVENT = new Event(getMiddleX(0, carStart), 2);
        Event END_EVENT = new Event(getMiddleX(time, carStart + carVelocity * (double) time), 3);
        if (START_EVENT.pos > END_EVENT.pos) {
            Event t = START_EVENT;
            START_EVENT = END_EVENT;
            END_EVENT = t;
            START_EVENT.type = 2;
            END_EVENT.type = 3;
        }

        double len = END_EVENT.pos - START_EVENT.pos;
        double speed = len / time;

        if (speed == 0) {
            for (int i = 0; i < columnCount; i++) {
                if (columnStarts[i] <= START_EVENT.pos && START_EVENT.pos <= columnStarts[i] + width) {
                    return 0;
                }
            }
            return time;
        }

        add(events, START_EVENT, events.length - 2);
        add(events, END_EVENT, events.length - 1);

        double answer = 0;
        boolean meStarted = false;
        double lastPos = events[0].pos;
        boolean currentOpened = true;
        for (Event e : events) {
            if (e.type == 2) {
                meStarted = true;
                if (currentOpened) {
                    lastPos = e.pos;
                }
            }
            if (e.type == 3) {
                if (currentOpened) {
                    answer += (e.pos - lastPos) / speed;
                }
                break;
            }
            if (e.type == 0) {
                currentOpened = false;
                if (meStarted) {
                    answer += (e.pos - lastPos) / speed;
                }
            }
            if (e.type == 1) {
                lastPos = e.pos;
                currentOpened = true;
            }
        }

        remove(events, START_EVENT, events.length);
        remove(events, END_EVENT, events.length - 1);
        return answer;
    }

    double getMiddleX(double me, double onRoad) {
        double h = yRoad + 1;
        double delta = (onRoad - me) / h;
        return me + delta;
    }

    void add(Event[] a, Event add, int at) {
        a[at] = add;
        while (at > 0 && a[at - 1].compareTo(a[at]) > 0) {
            Event e = a[at - 1];
            a[at - 1] = a[at];
            a[at] = e;
            at--;
        }
    }

    void remove(Event[] a, Event rem, int size) {
        for (int i = 0, j = 0; i < size; i++) {
            if (a[i] == rem) continue;
            a[j++] = a[i];
        }
        a[size - 1] = null;
    }

    class Event implements Comparable<Event> {
        double pos;
        int type;
        //0 - column start
        //1 - column end
        //2 - my start
        //3 - my end

        Event(double pos, int type) {
            this.pos = pos;
            this.type = type;
        }

        @Override
        public int compareTo(Event o) {
            int c = Double.compare(pos, o.pos);
            if (c == 0) c = Integer.compare(type, o.type);
            return c;
        }

        @Override
        public String toString() {
            return "Event{" +
                    "pos=" + pos +
                    ", type=" + type +
                    '}';
        }
    }

    int time;
    int width;
    int yRoad;
    int carVelocity;

    int columnCount;
    int[] columnStarts;

    int carCount;
    long[] carStarts;
}