Sha256: f83b357951c94a0c8c42eacdb74cdb161a465311d3f8337d5a060ecee1d752ac
Contents?: true
Size: 966 Bytes
Versions: 26
Compression:
Stored size: 966 Bytes
Contents
unless Array.method_defined? :combination
require 'backports/tools'
require 'enumerator'
class Array
def combination(num)
num = Backports.coerce_to_int(num)
return to_enum(:combination, num) unless block_given?
return self unless (0..size).include? num
# Implementation note: slightly tricky.
# Example: self = 1..7, num = 3
picks = (0...num).to_a # picks start at 0, 1, 2
max_index = ((size-num)...size).to_a # max (index for a given pick) is [4, 5, 6]
pick_max_pairs = picks.zip(max_index).reverse # pick_max_pairs = [[2, 6], [1, 5], [0, 4]]
leave = Proc.new{return self}
loop do
yield values_at(*picks)
move = pick_max_pairs.find(leave){|pick, max| picks[pick] < max}.first
new_index = picks[move] + 1
picks[move...num] = (new_index...(new_index+num-move)).to_a
end
end
end
end
Version data entries
26 entries across 26 versions & 2 rubygems