thealgorithms / python

All Algorithms implemented in Python

The Algorithms - Python

All algorithms implemented in Python - for education

Implementations are for learning purposes only. They may be less efficient than the implementations in the Python standard library. Use them at your discretion.

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Read through our Contribution Guidelines before you contribute.

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List of Algorithms

See our directory for easier navigation and a better overview of the project.

python's Issues

LCA problem

Hey, Can i include code for Lowest Common Ancestor algorithm for Directed Acyclic Graph (algorithm is based upon LCA problem to RMQ(Range Minimum Query) problem reduction (solving RMQ problem via sparse table), which has time complexity per query O(1) and memory complexity of O(N.log N) ?

typo error in data_structures/AVL/AVL.py

there is a misprint in AVL.py in (t.Preorden)

knapsack.py can be improved

knapsack.py fills up the entire 2D table. We can improve it by using memory functions.Which solve only subproblems which are needed

What if brackets have any string in-between?

here

What will happen if the input consists of more than just nested brackets, like a full source code.

python-函数问题讨论

Sync with Travis-CI

If you want previous merge to work, you need to sync this repository with Travis-CI.
I already had made request from my Travis-CI profile to this organization, you just need to grant it.

Logo Proposal

Greetings @TheAlgorithms ,

I'm a Graphic Designer interested in collaborating
with this project by delivering a free logo proposal
if this is something that interest this project, let me know

Cheers!
-Luigi.

test

I have a queryk

quicksort probabilistic guarantee

Hi,
I think your implementation of quicksort lacks randomizing of the input. If you shuffle it, you are almost guaranteed to not have O(n^2) time scenario.

/sorts/merge_sort_fastest.py is NOT fast at all

Hi @harshildarji & @yesIamHasi ,

Thanks for sharing algorithm source code and I really like them.

Just want to raise an issue on '/sorts/merge_sort_fastest.py' that it is not an merge_sort option as there are dependencies on python built-in functions - remove(), max() & min(), which makes 'merge_sort_fastest' like O(n^2) [ (n*(n+1)) / 2 * 2 as one max()/min() with remove()] instead of O(n log n).

For example, while sorting 50,000 random numbers with below list:
unsorted = random.sample(range(0, 100000), 50000)

The running result will be like:
(venv) $ time python3 merge_sort.py
real 0m0.361s
user 0m0.347s
sys 0m0.011s

(venv) $ time python3 merge_sort_fastest.py
real 0m49.306s
user 0m49.103s
sys 0m0.099s

thanks!
Tom

Add Dijkstra's shortest path algorithm in the graph section

Being one of the most common algorithm in the Graph set, it should be implemented.

I'd like to contribute by adding the Trie data structure

I'm working on a Trie implementation and a simple example looking up a word in a dictionary. Thinking about using the Dictionary.txt file in the other folder.

README.md - Quicksort average case performance

Readme says average case performance for quicksort is 0(n^2), but elsewhere, this is O(n log n).
https://en.wikipedia.org/wiki/Quicksort

Is this a bug in the docs? Or is average case performance for the version of quicksort in this repo actually O(n^2)?

Python 2 or Python 3 or both?

Is the code in this repo designed to run on Python 2 or on Python 3 or on both?

Codility solutions

Would anyone be interested in a PR for Codility solutions?

I'd like to contribute with scoring functions in ML

For algorithms in machine learnings, I'd like to start from adding some scoring functions.
Such as MSE, RMSE stuffs. Can I contribute?

server.py : Error

See the file here

Traceback (most recent call last):
File "/home/christian/Programmierung/GitHub/Python/server.py", line 29, in
t.bind()
File "/usr/lib/python2.7/socket.py", line 228, in meth
return getattr(self._sock,name)(*args)
TypeError: bind() takes exactly one argument (0 given)

The error above occures by python 2 and python 3.

The taste of selection_sort and merge_sort is not good.

All the sorting algorithms are implemented in Python using C++ thinking which makes the code execution time too high.
The current selection sort algorithm is 65% slower, merge_sort algorithm is 10^4 times slower.
Here's timeit result.

Here is a better taste of selection sort.
Here is a better taste of merge sort.
Tell me what you think about it?
Should I add it to TheAlgorithms/Python/sorts ?

Code runs in infinite loop to accept Tree elements

This code needs logic fix and libraries.

README.md not up to date

travis-ci

@h-darji why you removed python version 2.7 from travis.yml file? Many people are still using python ver 2.7.

Bug report for radix sort

Description

if the test case for radix_sort.py is [104, 203, 308, 401], the result would be [401, 203, 104, 308]

It's wrong!

The reason is that if the tmp is always 0 in one loop, it will exit the loop. In other words, If the same digit of all numbers is 0, then the result may be wrong. The similar example like:
Input: [2018, 33017, 24016]
Output: [24016, 33017, 2018]
Wrong again!!

Suggestion

Do not use maxLength as a loop variable because the value of maxLength is related to tmp.

I think that by finding the maximum value of the array and assigning it to max_digit, using another variable digit with an initial value of 1 as the loop variable, each loop digit is multiplied by 10, and exit the loops when the digit greater than max_digit, which can guarantee the correct number of loops.

And the complexity will be O(nk + n) . n is the size of input list and k is the digit length of the number.

No successful Travis builds in the last 4 months

https://travis-ci.org/TheAlgorithms/Python/builds

Merge sort best & average case O(n)?

https://github.com/TheAlgorithms/Python/blob/master/README.md#merge
Shouldn't it be O(n log n).

The Java repo is correct though:
https://github.com/TheAlgorithms/Java#merge

Invalid file name

file Graphs/A*.py has invalid file name, leading failure to sync this remote repository.
can anyone fix this file?

Tests

Hey, maybe it would be necessary to add a test for each algorithm. For those who need it do not want to test everything yourself :)

A new data structure proposal

Greetings @TheAlgorithms ,

I wish to contribute to this project by proposing to add a new data structure called Binary Indexed Tree.
How can i start ?
Any suggestions ?

regards,
Nikhil.

Use consistent directories and file naming

Currently, the directories and files don't follow a convention, some are snake_case, some PascalCase. We should stick to a convention.

2 Graph folders

There are 2 separate folder of Graph

1. Graph
2. Data Structures - > Graph

Merge them and keep the second one

bucket_sort

hello,where is "P26_InsertionSort" for bucket_sort.py?I can't run it.I am a player,you know.Thank you

May I add Elgamal security system algorithm to “cipher” directory?

Hello world! I’m Sang Young Park, a student studying cryptography at South Korea
By the way, may I add The Elgamal security system code using python to this awsome project?

Best regards, Sang Young

Typo in BinSearch

Line 113 & 115 in BinSearch have typos in them. It should be mid-1 and mid+1.
https://github.com/TheAlgorithms/Python/blob/master/searches/binary_search.py

if sorted_collection[midpoint] == item:
    midpoint
elif sorted_collection[midpoint] > item:
    binary_search_by_recursion(sorted_collection, item, left, right-1)
else:
    binary_search_by_recursion(sorted_collection, item, left+1, right)

should be

if sorted_collection[midpoint] == item:
    return midpoint
elif sorted_collection[midpoint] > item:
    return binary_search_by_recursion(sorted_collection, item, left, mid-1)
else:
    return binary_search_by_recursion(sorted_collection, item, mid+1, right)

Issue in importing SKLearn package in Jupyter notebook (Python code)

Hello folks,

I have problem in importing some packages. I need to know how and where could I install packages so I can import it in Jupyther Notebook?

e.g: I write this code in jupyther :
from sklearn.family import Model

and i got an error as shown bellow.

---

ModuleNotFoundError Traceback (most recent call last)
in ()
----> 1 from sklearn.family import Model

ModuleNotFoundError: No module named 'sklearn.family'

I installed the SKlearn package using python command prompt. However, I think there is no link between SKlearn package I have installed and the Jupyter notebook that I am using. How to solve it out?

I appreciate your responses.

Regards,
Mona

Sending Email by extracting xml content

I need python code which will watch for directory for XML files. Once the xml is generated, i need to send email to the persons. 'TO' email is dynamic and it would be available with 'BillingCode field in xml file which is generated. Also in mail body i need to use other xml fields.

Please suggest!

ProjectEuler -- Problem 1 -- solv4.py -- Error

The correct answer is 233168 the program displays 266333. See here

I like to work in AVL, PArtially ordered tree and A* is it anyone doing this actually?

Some files use print("", end="") from python 3.x which is not available by default in 2.x

I thought it was only one file at the beginning, but it seems that several files use this print statement, so from __future__ import print_function is needed for 2.x

Add demo gif to README

Disclaimer: This is a bot

It looks like your repo is trending. The github_trending_videos Instgram account automatically shows the demo gifs of trending repos in Github.

Your README doesn't seem to have any demo gifs. Add one and the next time the parser runs it will pick it up and post it on its Instagram feed. If you don't want to just close this issue we won't bother you again.

I would like to work on Numerical analysis algorithms such as LU decomposition, cholesky and so on, if you want to add it to your project.

Radix Sort broken in Python 3

In Python 3 radix sort is broken.

Traceback (most recent call last):
  File "radix_sort.py", line 30, in <module>
    radixsort(ar);
  File "radix_sort.py", line 14, in radixsort
    buckets[tmp % RADIX].append( i )
TypeError: list indices must be integers or slices, not float

I will fix it asap and submit a pull request.

Incorrect markdown

The markdown in README.md for Time-Compexity Graphs is not used correctly.
Should I send a PR for a fix ?

Non-pythonic code

Code shown in this repository is mostly non-pythonic. It doesn't follow any conventions from PEP8 and all algorithms have a lot of anti-patterns. For example, binary search as shown in Python docs -- https://docs.python.org/3/library/bisect.html#searching-sorted-lists.

I don't know the exact purpose of this repository, but it certainly doesn't show well-implemented basic algorithms in Python.

Travis CI

Add a .travis.yml file to this repository.
Refer to this doc https://docs.travis-ci.com/user/languages/python/

Longest Increasing Subsequence - in O(NlogN) #DynamicProgramming

I would like to add Dynamic programming code for LIS with complexity of O(NlogN)

Redundant parameters in SegmentTree

here st.query(1, 1, N, ...) the first three parameters are unnecessary. We are using class but not taking advantage of it.

The same thing is with other classes as well.

ProjectEuler -- Problem 1 -- solv2.py -- Error

For the Input 1000 I get 233366.4. The correct answer should be 233168
See file

The linklist in data_structure may has some issue

Adopt a more robust testing system

I find that tests are currently very limited in capability. And there are very few tests with each algorithm.

We should have more tests and an efficient testing mechanism.

Contribution

Hello,

My name is Iro Kafetzaki and I'm studying in the third year at the Athens University of Economics and Business in the Department of Management Science and Technology. In terms of a lesson called Software Engineering in Practise and as I'm interested in algorithms that can be used for operational research I would like to ask you if I can contribute to your project in the "searches" folder and contribute tabu search for a Traveling Salesman Problem -TSP written in python.

Thank you in advance.

Add a license for your repository

Hi!

I would request the owner of this repository to add a license. A license is useful to show if whether a user can use your code freely or not. If you do not have a license, a user may avoid to use your code (see here: http://choosealicense.com/no-license/).

I recommend using MIT license (http://choosealicense.com/licenses/mit/) so the user can tinker with the codes themselves. Also, by using this license, the user can't hold you liable if somehow they broke their computers using your example codes.