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Author: javaarchive

cowjump.java

@@ -0,0 +1,59 @@
+import java.io.*;
+import java.util.*;
+public class cowjump {
+	public static void testIntersections() {
+		assert Point.intersection(new Point(0,0), new Point(2,9), new Point(0,1), new Point(6,1))== true; 
+		assert Point.intersection(new Point(0,0), new Point(1,1), new Point(3,3), new Point(3,12))== false; 
+		System.out.println("All Tests OK!");
+	}
+	public static void main(String[] args) throws IOException{
+		// TODO Auto-generated method stub
+		//testIntersections();
+		BufferedReader f = new BufferedReader(new FileReader("cowjump.in"));
+		int N = Integer.parseInt(f.readLine());
+		Point[][] input = new Point[N][2];
+		//System.out.println(input[0][0]);
+		for(int i = 0; i < N; i ++) {
+			StringTokenizer st = new StringTokenizer(f.readLine());
+			input[i][0] = new Point(Integer.parseInt(st.nextToken()), Integer.parseInt(st.nextToken()));
+			input[i][1] = new Point(Integer.parseInt(st.nextToken()), Integer.parseInt(st.nextToken()));
+			for(int j = 0; j < i; j ++) {
+				if(Point.intersection(input[j][0], input[j][1], input[i][0], input[i][1])) {
+					PrintWriter pw = new PrintWriter("cowjump.out");
+					pw.println(i+1);
+					pw.close();
+					System.exit(0);
+				}
+			}
+		}
+	}
+
+}
+class Point{
+	int x,y;
+	public Point(int x,int y) {
+		this.x = x;
+		this.y = y;
+	}
+	public Point() {
+		this.x = 0;
+		this.y = 0;
+	}
+	static boolean intersection(Point a, Point b,Point c, Point d) {
+		Point E = new Point(b.x - a.x, b.y - a.y);
+		Point F = new Point(d.x - c.x, d.y - c.y);
+		Point P = new Point(-E.y, E.x);
+		Point Q = new Point(a.x - c.x, a.y - c.y);
+		double k = F.x * P.x + F.y * P.y;
+		if(k == 0) {
+			// Parallel
+			return false;
+		}
+		
+		double h = (Q.x * P.x + Q.y * P.y)/(k);
+		if(0 <= h && h <= 1) {
+			return true;
+		}
+		return false;
+	}
+}