Python

All Algorithms implemented in Python

Subscribe to updates I use Python


Statistics on Python

Number of watchers on Github 4064
Number of open issues 2
Average time to close an issue 6 days
Main language Python
Average time to merge a PR 3 days
Open pull requests 3+
Closed pull requests 10+
Last commit 9 months ago
Repo Created over 2 years ago
Repo Last Updated 9 months ago
Size 1.6 MB
Organization / Authorthealgorithms
Contributors4
Page Updated
Do you use Python? Leave a review!
View open issues (2)
View Python activity
View on github
Fresh, new opensource launches 🚀🚀🚀
Trendy new open source projects in your inbox! View examples

Subscribe to our mailing list

Evaluating Python for your project? Score Explanation
Commits Score (?)
Issues & PR Score (?)

The Algorithms - Python <!-- Build Status -->

All algorithms implemented in Python (for education)

These are for demonstration purposes only. There are many implementations of sorts in the Python standard library that are much better for performance reasons.

Sort Algorithms

Bubble

alt text

From Wikipedia: Bubble sort, sometimes referred to as sinking sort, is a simple sorting algorithm that repeatedly steps through the list to be sorted, compares each pair of adjacent items and swaps them if they are in the wrong order. The pass through the list is repeated until no swaps are needed, which indicates that the list is sorted.

Properties

  • Worst case performance O(n2)
  • Best case performance O(n)
  • Average case performance O(n2)
View the algorithm in action

Insertion

alt text

From Wikipedia: Insertion sort is a simple sorting algorithm that builds the final sorted array (or list) one item at a time. It is much less efficient on large lists than more advanced algorithms such as quicksort, heapsort, or merge sort.

Properties

  • Worst case performance O(n2)
  • Best case performance O(n)
  • Average case performance O(n2)
View the algorithm in action

Merge

alt text

From Wikipedia: In computer science, merge sort (also commonly spelled mergesort) is an efficient, general-purpose, comparison-based sorting algorithm. Most implementations produce a stable sort, which means that the implementation preserves the input order of equal elements in the sorted output. Mergesort is a divide and conquer algorithm that was invented by John von Neumann in 1945.

Properties

  • Worst case performance O(n log n)
  • Best case performance O(n)
  • Average case performance O(n)
View the algorithm in action

Quick

alt text

From Wikipedia: Quicksort (sometimes called partition-exchange sort) is an efficient sorting algorithm, serving as a systematic method for placing the elements of an array in order.

Properties

  • Worst case performance O(n2)
  • Best case performance O(n log n) or O(n) with three-way partition
  • Average case performance O(n log n)
View the algorithm in action

Selection

alt text

From Wikipedia: The algorithm divides the input list into two parts: the sublist of items already sorted, which is built up from left to right at the front (left) of the list, and the sublist of items remaining to be sorted that occupy the rest of the list. Initially, the sorted sublist is empty and the unsorted sublist is the entire input list. The algorithm proceeds by finding the smallest (or largest, depending on sorting order) element in the unsorted sublist, exchanging (swapping) it with the leftmost unsorted element (putting it in sorted order), and moving the sublist boundaries one element to the right.

Properties

  • Worst case performance O(n2)
  • Best case performance O(n2)
  • Average case performance O(n2)
View the algorithm in action

Shell

alt text

From Wikipedia: Shellsort is a generalization of insertion sort that allows the exchange of items that are far apart. The idea is to arrange the list of elements so that, starting anywhere, considering every nth element gives a sorted list. Such a list is said to be h-sorted. Equivalently, it can be thought of as h interleaved lists, each individually sorted.

Properties

  • Worst case performance O(nlog2 2n)
  • Best case performance O(n log n)
  • Average case performance depends on gap sequence
View the algorithm in action

Time-Complexity Graphs

Comparing the complexity of sorting algorithms (Bubble Sort, Insertion Sort, Selection Sort)

Complexity Graphs


Search Algorithms

Linear

alt text

From Wikipedia: linear search or sequential search is a method for finding a target value within a list. It sequentially checks each element of the list for the target value until a match is found or until all the elements have been searched. Linear search runs in at worst linear time and makes at most n comparisons, where n is the length of the list.

Properties

  • Worst case performance O(n)
  • Best case performance O(1)
  • Average case performance O(n)
  • Worst case space complexity O(1) iterative

Binary

alt text

From Wikipedia: Binary search, also known as half-interval search or logarithmic search, is a search algorithm that finds the position of a target value within a sorted array. It compares the target value to the middle element of the array; if they are unequal, the half in which the target cannot lie is eliminated and the search continues on the remaining half until it is successful.

Properties

  • Worst case performance O(log n)
  • Best case performance O(1)
  • Average case performance O(log n)
  • Worst case space complexity O(1)

Ciphers

Caesar

alt text
In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code or Caesar shift, is one of the simplest and most widely known encryption techniques.
It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, D would be replaced by A, E would become B, and so on.
The method is named after Julius Caesar, who used it in his private correspondence.
The encryption step performed by a Caesar cipher is often incorporated as part of more complex schemes, such as the Vigenre cipher, and still has modern application in the ROT13 system. As with all single-alphabet substitution ciphers, the Caesar cipher is easily broken and in modern practice offers essentially no communication security.

Source: Wikipedia

Vigenre

The Vigenre cipher is a method of encrypting alphabetic text by using a series of interwoven Caesar ciphers based on the letters of a keyword. It is a form of polyalphabetic substitution.
The Vigenre cipher has been reinvented many times. The method was originally described by Giovan Battista Bellaso in his 1553 book La cifra del. Sig. Giovan Battista Bellaso; however, the scheme was later misattributed to Blaise de Vigenre in the 19th century, and is now widely known as the Vigenre cipher.
Though the cipher is easy to understand and implement, for three centuries it resisted all attempts to break it; this earned it the description le chiffre indchiffrable(French for 'the indecipherable cipher'). Many people have tried to implement encryption schemes that are essentially Vigenre ciphers. Friedrich Kasiski was the first to publish a general method of deciphering a Vigenre cipher in 1863.

Source: Wikipedia

Transposition

In cryptography, a transposition cipher is a method of encryption by which the positions held by units of plaintext (which are commonly characters or groups of characters) are shifted according to a regular system, so that the ciphertext constitutes a permutation of the plaintext. That is, the order of the units is changed (the plaintext is reordered).
Mathematically a bijective function is used on the characters' positions to encrypt and an inverse function to decrypt.

Source: Wikipedia
Python open pull requests (View All Pulls)
  • Adds Trees Data Structure
  • Update binary_tree_traversals.py
  • Updated the binary_tree_traversals.py with fix
Python questions on Stackoverflow (View All Questions)
  • Reading in file block by block using specified delimiter in python
  • Changing the value of range during iteration in Python
  • How to parse temporal expressions (esp. time ranges), Python?
  • Python 3.5 Windows cannot run Rodeo example?
  • Self executable python file
  • Python requests get token and post it elsewhere
  • Code works in Java but not Python?
  • How to properly decode .wav with Python
  • Sort python dictionary for keys, split it and create a JSON Array from it
  • Solving CodingBat brick making puzzle in Python
  • Python Super: calling a base class method which contains another base class method that is overriden by derived class
  • What is the difference between the widgets of tkinter and tkinter.ttk in Python?
  • Object and instances in Python
  • Python Ref Counts to Object
  • Multithread python requests
  • How to correctly countdown with Python 3 after asking user for 'wakeup' time?
  • Python manual call to descriptor ignored
  • How to count objects in image using python?
  • How do I pass variables between two different python scripts I have
  • Python nested lambda expression still confused and couldn't understandable. please explain the following example
  • python seaborn colormap steps
  • Pandas read_html skips header of table (python)
  • KIVY - Python Keep doing while button is pressed
  • Encoding and Decoding in Python
  • print UTF-8 character in Python 2.7
  • initialization of multiarray raised unreported exception python
  • use nodebox as a module for python 3.5
  • How to verify permissions for file systems are in read only using python?
  • How to split a statement based on dots ('.'), while excluding dots inside angular brackets(< . >) using regular expressions in python?
  • Python Selenium:: Element is Currently Invisible
Python list of languages used
More projects by TheAlgorithms View all
Other projects in Python