mklbtz

# O(nk)
class Array
  def unzip ary
    return [] if ary.empty?
    count = ary.first.count
    (0...count).map { |i| 
      ary.map { |tuple| 
        raise 'inconsistent tuple size' if tuple.count != count
        tuple[i] 
      }

mklbtz

# The MIT License (MIT)
#
# Copyright (c) 2015 Michael Bates
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:

mklbtz

// Here, I’ve added a function to Array called `partition`. 
// In short, the function will partition the Array into a Dictionary based on a function 
// which takes an Element of the Array and returns its corresponding Key into the Dictionary.

extension Array {
  func partition<Key>(key: (Element)->Key) -> [Key: [Element]] {
  var groups = [Key: [Element]]()
    for element in self {
      let key = key(element)
      var group = groups[key] ?? [Element]()