September 2017 Update

Task/Non-continuous-subsequences/CoffeeScript/non-continuous-subsequences-1.coffee

@@ -1,57 +0,0 @@
-is_contigous_binary = (n) ->
-  # return true if binary representation of n is
-  # of the form 1+0+
-  # examples:
-  #     0 true
-  #     1 true
-  #   100 true
-  #   110 true
-  #  1001 false
-  #  1010 false
-
-  # special case zero, or you'll get an infinite loop later
-  return true if n == 0
-
-  # first remove 0s from end
-  while n % 2 == 0
-    n = n / 2
-
-  # next, take advantage of the fact that a continuous
-  # run of 1s would be of the form 2^n - 1
-  is_power_of_two(n + 1)
-
-is_power_of_two = (m) ->
-  while m % 2 == 0
-    m = m / 2
-  m == 1
-
-seq_from_bitmap = (arr, n) ->
-  # grabs elements from array according to a bitmap
-  # e.g. if n == 13 (1101), and arr = ['a', 'b', 'c', 'd'],
-  # then return ['a', 'c', 'd'] (flipping bits to 1011, so
-  # that least significant bit comes first)
-  i = 0
-  new_arr = []
-  while n > 0
-    if n % 2 == 1
-      new_arr.push arr[i]
-      n -= 1
-    n /= 2
-    i += 1
-  new_arr
-
-non_contig_subsequences = (arr) ->
-  # Return all subsqeuences from an array that have a "hole" in
-  # them.  The order of the subsequences is not specified here.
-
-  # This algorithm uses binary counting, so it is limited to
-  # small lists, but large lists would be unwieldy regardless.
-  bitmasks = [0...Math.pow(2, arr.length)]
-  (seq_from_bitmap arr, n for n in bitmasks when !is_contigous_binary n)
-
-arr = [1,2,3,4]
-console.log non_contig_subsequences arr
-for n in [1..10]
-  arr = [1..n]
-  num_solutions = non_contig_subsequences(arr).length
-  console.log "for n=#{n} there are #{num_solutions} solutions"

Task/Non-continuous-subsequences/CoffeeScript/non-continuous-subsequences-2.coffee

@@ -1,16 +0,0 @@
-> coffee non_contig_subseq.coffee
-[ [ 1, 3 ],
-  [ 1, 4 ],
-  [ 2, 4 ],
-  [ 1, 2, 4 ],
-  [ 1, 3, 4 ] ]
-for n=1 there are 0 solutions
-for n=2 there are 0 solutions
-for n=3 there are 1 solutions
-for n=4 there are 5 solutions
-for n=5 there are 16 solutions
-for n=6 there are 42 solutions
-for n=7 there are 99 solutions
-for n=8 there are 219 solutions
-for n=9 there are 466 solutions
-for n=10 there are 968 solutions