Inspired by Python's heapq module, Heapify is a Ruby library that provides methods to transform an array into a min heap. A min heap is a binary tree where the parent node is less than or equal to its children.
The API below differs from textbook heap algorithms in two aspects: (a) We use zero-based indexing. This makes the relationship between the index for a node and the indexes for its children slightly less obvious, but is more suitable since Ruby uses zero-based indexing. (b) Our pop method returns the smallest item, not the largest (called a “min heap” in textbooks; a “max heap” is more common in texts because of its suitability for in-place sorting).
These two make it possible to view the heap as a regular Ruby list without surprises: heap[0] is the smallest item, and heap.sort maintains the heap invariant!
Using an Array allows random access to the heap's elements. If we use a Heap class, we cannot allow random access while guaranteeing the heap invariant. For the same reason, we cannot efficiently implement Enumerable for a Heap class, but with the Array, we don't have to worry about that. It's obvious that it's the user's responsibility to maintain the heap. This makes using an Array much more flexible.
Add this line to your application's Gemfile:
gem 'heapify'And then execute:
bundle installOr install it yourself as:
gem install heapifyHeapify extends the Array class with the following methods:
Transforms an array into a heap in-place. It has a time complexity of O(n) and a space complexity of O(1).
heap = [4, 1, 3, 2, 16, 9, 10, 14, 8, 7]
heap.heapify # => [1, 2, 3, 4, 7, 9, 10, 14, 8, 16]This method adds an element to the heap. It has a time complexity of O(log n) and a space complexity of O(1).
heap = [1, 2, 3, 4, 7, 9, 10, 14, 8, 16]
heap.heap_push(5) # array => [1, 2, 3, 4, 5, 9, 10, 14, 8, 7, 16]This method removes the smallest element from the heap and returns it. It has a time complexity of O(log n) and a space complexity of O(1).
heap = [1, 2, 3, 4, 7, 9, 10, 14, 8, 16]
heap.heap_pop # => 1Bug reports and pull requests are welcome on GitHub at https://github.com/garrisonj/heapify. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.
The gem is available as open source under the terms of the MIT License.
Everyone interacting in the Heapify project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.