挑战程序竞赛系列（84）：3.6极限情况（1）

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.StringTokenizer;

public class Main{

    String INPUT = "./data/judge/201709/P1981.txt";

    public static void main(String[] args) throws IOException {
        new Main().run();
    }

    static final int MAX_N = 302;

    class P {
        double x;
        double y;
        P(double x, double y){
            this.x = x;
            this.y = y;
        }
    }

    class PolarAngle implements Comparable<PolarAngle>{

        double  angle;
        boolean flag;
        PolarAngle(double angle, boolean flag){
            this.angle = angle;
            this.flag  = flag;
        }
        @Override
        public int compareTo(PolarAngle that) {
            return Double.compare(this.angle, that.angle);
        }
    }

    P[] points = new P[MAX_N];
    PolarAngle[] pa = new PolarAngle[2 * MAX_N];

    int N;
    int ans;

    double dist(P a, P b) {
        double dx = a.x - b.x;
        double dy = a.y - b.y;
        return Math.sqrt(dx * dx + dy * dy);
    }

    void solve() {
        ans = 1;
        for (int i = 0; i < N; ++i) {
            int m = 0;
            for (int j = 0; j < N; ++j) {
                double d = 0;
                if (i != j && (d = dist(points[i], points[j])) <= 2.0) {
                    double theta = Math.acos(d / 2);
                    double phi   = Math.atan2(points[j].y - points[i].y, points[j].x - points[i].x);
                    pa[m++] = new PolarAngle(phi - theta, true);  // start
                    pa[m++] = new PolarAngle(phi + theta, false); // end;
                }
            }

            Arrays.sort(pa, 0, m);

            int sum = 1;
            for (int j = 0; j < m; ++j) {
                if (pa[j].flag) {
                    sum ++;
                }
                else {
                    sum --;
                }
                ans = Math.max(ans, sum);
            }
        }
    }

    void read() {
        while (true) {
            N = ni();
            if (N == 0) break;
            for (int i = 0; i < N; ++i) {
                points[i] = new P(nd(), nd());
            }
            ans = 0;
            solve();
            out.println(ans);
        }
    }

    FastScanner in;
    PrintWriter out;

    void run() throws IOException {
        boolean oj;
        try {
            oj = ! System.getProperty("user.dir").equals("F:\\java_workspace\\leetcode");
        } catch (Exception e) {
            oj = System.getProperty("ONLINE_JUDGE") != null;
        }

        InputStream is = oj ? System.in : new FileInputStream(new File(INPUT));
        in = new FastScanner(is);
        out = new PrintWriter(System.out);
        long s = System.currentTimeMillis();
        read();
        out.flush();
        if (!oj){
            System.out.println("[" + (System.currentTimeMillis() - s) + "ms]");
        }
    }

    public boolean more(){
        return in.hasNext();
    }

    public int ni(){
        return in.nextInt();
    }

    public long nl(){
        return in.nextLong();
    }

    public double nd(){
        return in.nextDouble();
    }

    public String ns(){
        return in.nextString();
    }

    public char nc(){
        return in.nextChar();
    }

    class FastScanner {
        BufferedReader br;
        StringTokenizer st;
        boolean hasNext;

        public FastScanner(InputStream is) throws IOException {
            br = new BufferedReader(new InputStreamReader(is));
            hasNext = true;
        }

        public String nextToken() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (Exception e) {
                    hasNext = false;
                    return "##";
                }
            }
            return st.nextToken();
        }

        String next = null;
        public boolean hasNext(){
            next = nextToken();
            return hasNext;
        }

        public int nextInt() {
            if (next == null){
                hasNext();
            }
            String more = next;
            next = null;
            return Integer.parseInt(more);
        }

        public long nextLong() {
            if (next == null){
                hasNext();
            }
            String more = next;
            next = null;
            return Long.parseLong(more);
        }

        public double nextDouble() {
            if (next == null){
                hasNext();
            }
            String more = next;
            next = null;
            return Double.parseDouble(more);
        }

        public String nextString(){
            if (next == null){
                hasNext();
            }
            String more = next;
            next = null;
            return more;
        }

        public char nextChar(){
            if (next == null){
                hasNext();
            }
            String more = next;
            next = null;
            return more.charAt(0);
        }
    }
}