挑战程序竞赛系列（83）：3.6计算几何基础

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.Map;
import java.util.StringTokenizer;

public class Main{

    String INPUT = "./data/judge/201709/P1127.txt";

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

    class P {

        static final double EPS = 1e-10;

        double x;
        double y;

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

        P add(P a) {
            return new P(add(x, a.x), add(y, a.y));
        }

        P sub(P a) {
            return new P(add(x, -a.x), add(y, -a.y));
        }

        P mul(P a) {
            return new P(x * a.x, y * a.y);
        }

        double dot(P a) {
            return add(x * a.x,  y * a.y);
        }

        double det(P a) {
            return add(x * a.y, -y * a.x);
        }

        @Override
        public String toString() {
            return "(" + x + "," + y + ")";
        }

        public double add(double a, double b) {
            if (Math.abs(a + b) < EPS * (Math.abs(a) + Math.abs(b))) return 0;
            return a + b;
        }
    }

    boolean onSeg(P p1, P p2, P q) {
        return p1.sub(q).det(p2.sub(q)) == 0 && p1.sub(q).dot(p2.sub(q)) <= 0;
    }

    P intersection(P p1, P p2, P q1, P q2) {
        double fz = q2.sub(q1).det(q1.sub(p1));
        double fm = q2.sub(q1).det(p2.sub(p1));
        P q = p2.sub(p1);
        q = new P(fz / fm * q.x, fz / fm * q.y);
        return p1.add(q);
    }

    void read() {
        while (true) {
            int N = ni();
            if (N == 0) break;

            P[] p = new P[N];
            P[] q = new P[N];

            for (int i = 0; i < N; ++i) {
                p[i] = new P(nd(), nd());
                q[i] = new P(nd(), nd());
            }

            boolean[][] map = new boolean[N][N];
            for (int i = 0; i < N; ++i) {
                map[i][i] = true;
                for (int j = i + 1; j < N; ++j) {
                    if (p[i].sub(q[i]).det(p[j].sub(q[j])) == 0) {
                        map[i][j] = map[j][i] = onSeg(p[i], q[i], p[j])
                                                || onSeg(p[i], q[i], q[j])
                                                || onSeg(p[j], q[j], p[i])
                                                || onSeg(p[j], q[j], q[i]);
                    }
                    else {
                        P r = intersection(p[i], q[i], p[j], q[j]);
                        map[i][j] = map[j][i] = onSeg(p[i], q[i], r) && onSeg(p[j], q[j], r);
                    }
                }
            }

            for (int k = 0; k < N; ++k) {
                for (int i = 0; i < N; ++i) {
                    for (int j = 0; j < N; ++j) {
                        map[i][j] |= map[i][k] && map[k][j];
                    }
                }
            }

            while (true) {
                int a = ni();
                int b = ni();
                if (a + b == 0) break;
                a --;
                b --;
                out.println(map[a][b] ? "CONNECTED" : "NOT CONNECTED");
            }
        }
    }

    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);
        }
    }
}