Submission #732166

#	Time	Username	Problem	Language	Result	Execution time	Memory
732166		williampsun	Mobile (BOI12_mobile)	Java	25 / 100	1076 ms	131072 KiB

mobile

import java.io.*;
import java.util.*;

public class mobile {

    static int N;
    static int L;
    static ArrayList<Coordinate> coordinates;

    public static void main(String[] args) throws IOException {
        BufferedReader br;
        PrintWriter out;
        StringTokenizer st;
        try {
            br = new BufferedReader(new FileReader("highcard.in"));
            out = new PrintWriter(new BufferedWriter(new FileWriter("highcard.out")));
            st = new StringTokenizer(br.readLine());
        } catch (Exception e) {
            br = new BufferedReader(new InputStreamReader(System.in));
            out = new PrintWriter(System.out);
            st = new StringTokenizer(br.readLine());
        }

        N = Integer.parseInt(st.nextToken());
        L = Integer.parseInt(st.nextToken());

        coordinates = new ArrayList<>();
        for(int i = 0; i < N; i++) {
            st = new StringTokenizer(br.readLine());
            coordinates.add(new Coordinate(Integer.parseInt(st.nextToken()), Integer.parseInt(st.nextToken())));
        }

        double left = 0;
        double right = 1500000000;
        double answer = 0;
        do {
//            System.out.println(left + " " + right);
            double mid = (left + right) / 2;
            boolean working = works(mid);
            if (working) {
                answer = mid;
                left = mid;
            } else {
                right = mid;
            }
        } while (Math.abs(left - right) > 0.0001);

        out.print(answer);
        out.close();
    }

    static boolean works(double radius) {
        ArrayList<Intercept> intercepts = new ArrayList<>();
        int id = 0;
        for(Coordinate c : coordinates) {
            double[] theseInter = getIntercepts(c.x, c.y, radius);
            if(theseInter.length == 2) {
                intercepts.add(new Intercept(Math.min(theseInter[0], theseInter[1]), 1, id));
                intercepts.add(new Intercept(Math.max(theseInter[0], theseInter[1]), 2, id));
                id++;
            } else if (theseInter.length == 1) {
                intercepts.add(new Intercept(theseInter[0], 0, id));
                id++;
            }
        }

        intercepts.sort(new Compare());
        int numCircles = 0;
        for (Intercept intercept : intercepts) {
            if (intercept.x >= 0 && intercept.x <= L) {
                if(numCircles == 0 || (numCircles == 1 && intercept.type == 2)) {
                    return true;
                }
            }

            if (intercept.type == 1) {
                numCircles++;
            } else if (intercept.type == 2) {
                numCircles--;
            }
        }

        return intercepts.size() == 0;
    }

    static double[] getIntercepts(double h, double k, double radius) {
        if(radius * radius - k * k > 0) {
            double sqrt = Math.sqrt(radius * radius - k * k);
            return new double[] {sqrt + h, -sqrt + h};
        } else if (radius * radius - k * k == 0) {
            return new double[] {h};
        } else {
            return new double[] {};
        }
    }

    static class Coordinate {
        int x;
        int y;

        public Coordinate(int x, int y) {
            this.x = x;
            this.y = y;
        }
    }

    static class Intercept {
        double x;
        int type;
        int id;

        public Intercept(double x, int t, int id) {
            this.x = x;
            type = t;
            this.id = id;
        }
    }

    static class Compare implements Comparator<Intercept> {
        @Override
        public int compare(Intercept o1, Intercept o2) {
            if(o1.x < o2.x) {
                return -1;
            } else if (o1.x == o2.x) {
                return 0;
            }
            return 1;
        }
    }
}

• Subtask 1: 4 / 4
• Subtask 2: 4 / 4
• Subtask 3: 4 / 4
• Subtask 4: 4 / 4
• Subtask 5: 4 / 4
• Subtask 6: 5 / 5
• Subtask 7: 0 / 5
• Subtask 8: 0 / 5
• Subtask 9: 0 / 5
• Subtask 10: 0 / 5
• Subtask 11: 0 / 5
• Subtask 12: 0 / 5
• Subtask 13: 0 / 5
• Subtask 14: 0 / 5
• Subtask 15: 0 / 5
• Subtask 16: 0 / 5
• Subtask 17: 0 / 5
• Subtask 18: 0 / 5
• Subtask 19: 0 / 5
• Subtask 20: 0 / 5
• Subtask 21: 0 / 5