chadbrewbaker

def cat (letter, strlist)
  strlist.each_index{|i|  strlist[i] = letter+strlist[i]       }
		strlist
end

def dna(len)
	if (len ==1)
		#return ["a", "t", "c","g"]
		return ["a", "t"]
	end

chadbrewbaker

#Demonstration of how to keep the product of a queue over a semigroup in amortized O(1) time

arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

inbox = []
inprod =[]
outbox = []
outprod = []

chadbrewbaker

require 'rubygems'
require 'watir'
$browser = Watir::Browser.new
$browser.maximize

$browser.goto 'http://www.fbi.gov/wanted/topten/topten-history'

$browser.spans(:class, "blackgraphtx").each{|elt|
  puts elt.text
}

chadbrewbaker

# Gist to go with http://www.austinrochford.com/posts/2013-10-28-median-of-medians.html
# Chad Brewbaker   10/28/2013
#  https://news.ycombinator.com/item?id=6628474

def median_5(list, i = list.length/2)
  return list.sort[i]
end

def median(list, i = list.length/2)
  if (list.length <= 5)

chadbrewbaker

fibs = Enumerator.new do |yielder|
   a = b = 1
   yielder.yield 1
   yielder.yield 1
   (0..1.0/0).each do |number|
      ret = a + b
      b = a
      a = ret
      yielder.yield ret
   end

chadbrewbaker

(0..6).each do |i|
    [1,2,3,4,5,6].combination(i).each{ |x|
      puts x.inspect
      #test if this subset matches predicate
    }
end

chadbrewbaker

# Hook and shortcut from  AN EFFICIENT PARALLEL BICONNECTIVITY ALGORITHM
#Tarjan and Vishkin
# http://www.umiacs.umd.edu/users/vishkin/TEACHING/ENEE759KS12/TV85.pdf
def partitions(trans)
  parent =Array.new()
  0.upto(trans.length-1) do |index|
    parent.push(index)
  end
  0.upto(trans.length-1) do |outer_index|
    0.upto(trans.length-1) do |index|

chadbrewbaker

#Ruby code for studying locally k-consistent magmas.
# Any permutation of k elements will multiply to the same value, but may not for k+1 elements


#triangular numbers, the number of entries above the diagonal in an nxn matrix
#http://oeis.org/A000217
triangulars = Enumerator.new do |yielder|
  n =0
  yielder.yield n
  while true

chadbrewbaker

#Chad Brewbaker 1/13/2014
#Counting the number of insert delete binary search trees
#http://cstheory.stackexchange.com/questions/20533/height-of-randomly-built-binary-search-tree-by-insert-and-delete?noredirect=1#comment54289_20533
# Seems to be  http://oeis.org/A000680

def legal_tree(arr)
  1.upto(arr.length/2) do  |i|
     ins=   arr.rindex([i, 0].to_s)
     del= arr.rindex([i, 1].to_s)
    if ins > del

chadbrewbaker

#Worksheet for fast factorial algorithms, see http://cstheory.stackexchange.com/questions/20594/factoriality-testing-algorithms-and-their-efficiency
#Chad Brewbaker
#January 15, 2014

#http://www.cecm.sfu.ca/personal/pborwein/PAPERS/P29.pdf
#http://www.luschny.de/math/factorial/FastFactorialFunctions.htm
#http://cs.stackexchange.com/questions/14456/factorial-algorithm-more-efficient-than-naive-multiplication

require 'benchmark'
require 'prime'