ksgifford / data-structures

data-structures

This repository contains sample code for a number of classic data structures implemented in Python.

Use the Doubly Linked List or cases where a user may need to reference a previous item in the list from any given item, or where a user may need to iterate through the list in reverse order. Otherwise, use the slightly faster Singly Linked List.

Singly Linked List: Module linked_list.py contains a recursively generated linked list class (Linked_List).

Stack: Module stack.py leverages the linked_list module to build methods for generating a stack, as well as adding and removing items.

Doubly Linked List: Module dbl_linked_list.py contains a DblLinkedList class with pop, shift, insert, append and remove methods. It also contains a Node class, which DblLinkedList uses to hold its values.

Queue: Module new_queue.py contains a Queue class with enqueue, dequeue, and size methods, as well as a peek method that allows the user to get the value of the next item in the queue without popping it. The Queue class imports the DblLinkedList class described above, and most of its methods are composed from this class.

Deque: Module new_deque.py contains a Deque class with methods for appending to both ends of the deque, removing items from each end of the deque, "peeking" at the values of the items on each end, and calculating the size of the deque. The Deque class imports the DblLinkedList class, and most of its methods are composed from this class.

BinHeap: Module binheap.py contains a BinHeap class which sorts itself in binary heap fashion. Each node has two children, both of which must be of lesser value than the parent. The class has a pop method which removes the root at the top of the heap, and a push which appends a new value to the end of the heap. In both cases, the heap immediately re-arranges itself.

PriorityQueue: Module priorityq.py defines a PriorityQ class which sorts contents by the priority with which they were added. In Queue style, it then orders items by the order in which they were added (first in, first out). It has an insert method to add to the Priority Queue, and a pop method to remove and return the first item by priority. The peek method shows this same value.

Resources:

https://www.codefellows.org/blog/implementing-a-singly-linked-list-in-python

http://interactivepython.org/runestone/static/pythonds/BasicDS/ImplementinganUnorderedListLinkedLists.html

http://stackoverflow.com/questions/31333462/finding-the-length-of-a-linked-list-in-python

https://en.wikipedia.org/wiki/Linked_list