Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An Algorithm for Finding Convex Hulls of Planar Point Sets   This paper presents an alternate choice of computing the convex hulls (CHs)
for planar point sets. We firstly discard the interior points and then sort the
remaining vertices by x- / y- coordinates separately, and later create a group
ofquadrilaterals (e-Quads) recursively according to the sequences ofthe sorted
lists of points. Finally, the desired CH is built based on a simple polygon
derived from all e-Quads. Besides the preprocessing for original planar point
sets, this algorithm has another mechanism of discarding interior point when
form e-Quads and assemble the simple polygon. Compared with three popular CH
algorithms, the proposed algorithm can generate CHs faster thanthe three but
has a penalty in space cost.

31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin
16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
28
The categories of this paper are: alg-geom
6
The categories of this paper are: astro-ph
36
The categories of this paper are: cmp-lg
9
The categories of this paper are: nlin
18
The categories of this paper are: econ
22
The categories of this paper are: chao-dyn
25
The categories of this paper are: patt-sol