
ZOJ Problem Set  1369
The art galleries of the new and very futuristic building of the Center for Balkan Cooperation have the form of polygons (not necessarily convex). When a big exhibition is organized, watching over all of the pictures is a big security concern. Your task is that for a given gallery to write a program which finds the surface of the area of the floor, from which each point on the walls of the gallery is visible. On the figure 1. a map of a gallery is given in some coordinate system. The area wanted is shaded on the figure 2.
The number of tasks T that your program have to solve will be on the first row of the input file. Input data for each task start with an integer N, 5 <= N <= 1500. Each of the next N rows of the input will contain the coordinates of a vertex of the polygon  two integers that fit in 16bit integer type, separated by a single space. Following the row with the coordinates of the last vertex for the task comes the line with the number of vertices for the next test and so on.
80.00 Source: Southeast Europe 2002 