Convex Hull in Ruby

Convex Hull

in Ruby

Welcome to the Convex Hull in Ruby page! Here, you'll find the source code for this program as well as a description of how the program works.

Current Solution

# frozen_string_literal: true

USAGE = 'Usage: please provide at least 3 x and y coordinates as separate lists (e.g. "100, 440, 210")'

def usage!
  warn USAGE
  exit 1
end

def parse_list(str)
  str.split(",").map { Integer(it.strip) }
rescue ArgumentError, NoMethodError
  usage!
end

def cross(o, a, b)
  (a[0] - o[0]) * (b[1] - o[1]) -
    (a[1] - o[1]) * (b[0] - o[0])
end

def build_hull(points)
  hull = []

  points.each do |p|
    hull.pop while hull.size >= 2 && cross(hull[-2], hull[-1], p) <= 0
    hull << p
  end

  hull
end

def convex_hull(points)
  points = points.sort

  lower = build_hull(points)
  upper = build_hull(points.reverse)

  lower + upper[1..-2]
end

x_str, y_str = ARGV
usage! if x_str.nil? || y_str.nil?

x = parse_list(x_str)
y = parse_list(y_str)

usage! if x.size != y.size || x.size < 3

points = x.zip(y)

convex_hull(points).each do |x, y|
  puts "(#{x}, #{y})"
end

Convex Hull in Ruby was written by:

• Ștefan-Iulian Alecu

If you see anything you'd like to change or update, please consider contributing.

How to Implement the Solution

No 'How to Implement the Solution' section available. Please consider contributing.

How to Run the Solution

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