ZOJ Problem Set - 1081
Statement of the Problem
Several drawing applications allow us to draw polygons and almost all of them allow us to fill them with some color. The task of filling a polygon reduces to knowing which points are inside it, so programmers have to colour only those points.
You're expected to write a program which tells us if a given point lies inside
a given polygon described by the coordinates of its vertices. You can assume
that if a point is in the border of the polygon, then it is in fact inside the
The input file may contain several instances of the problem. Each instance consists of: (i) one line containing integers N, 0 < N < 100 and M, respectively the number of vertices of the polygon and the number of points to be tested. (ii) N lines, each containing a pair of integers describing the coordinates of the polygon's vertices; (iii) M lines, each containing a pair of integer coordinates of the points which will be tested for "withinness" in the polygon.
You may assume that: the vertices are all distinct; consecutive vertices in
the input are adjacent in the polygon; the last vertex is adjacent to the first
one; and the resulting polygon is simple, that is, every vertex is incident
with exactly two edges and two edges only intersect at their common endpoint.
The last instance is followed by a line with a 0 (zero).
For the ith instance in the input, you have to write one line in the output
with the phrase "Problem i:", followed by several lines, one for each
point tested, in the order they appear in the input. Each of these lines should
read "Within" or "Outside", depending on the outcome of
the test. The output of two consecutive instances should be separated by a blank
Source: South America 2001