ZOJ Problem Set - 2741
Offside is a very important law in a soccer game. We can find the details of the law from the official web-site of FIFA (Federation Internationale de Football Association), shown as below.
Your task is to determine whether a player is in an offside position, given all the positions of players and the ball. To make the problem easier, we assume the game field is always in the size of 100*70 and the coordinate of the field center is (0, 0), as shown in the following picture. Furthermore, we assume the goal on the line from (-50,-35) to (-50,35) is ours and the opponent's goal line is between (50,-35) and (50,35). Note that the central line belongs to both halves.
The input consists of several test cases, with each case standing in a single line. In each case, there are several coordinates in the format (x,y) where -50 <= x <= 50 and -35 <= y <= 35, seperated by a single space. The first coordinate represents the player's position and the second one indicates the ball. The following coordinates are the opponents' locations. The number of opponents in field is 2 at the least and 11 at the most.
Proceed until the end of file.
Print "Offside" on a single line if the player is in the offside position or "PlayOn" if not.
(30,10) (20,-5) (45,0) (25,12) (-20,30) (30,10) (20,-5) (45,0) (25,12) (30,12) (-20,30)
Author: JIANG, Hao
Source: Zhejiang Provincial Programming Contest 2006, Preliminary