### Index

* [Competitive Programming](#competitive-programming)
* [CTF Capture the Flag](#capture-the-flag)
* [Data science](#data-science)
* [Information security](#information-security)
* [Problem Sets](#problem-sets)


### Competitive Programming

* [4Clojure](http://www.4clojure.com)
* [A2 Online Judge](https://a2oj.com)
* [APL Problem Solving Competition](https://contest.dyalog.com)
* [AtCoder](https://atcoder.jp)
* [beecrowd](https://www.beecrowd.com.br)
* [Binary Search](https://binarysearch.com)
* [Caribbean Online Judge](http://coj.uci.cu)
* [COCI](https://hsin.hr/coci/)
* [Codeabbey](http://www.codeabbey.com)
* [Codechef](https://www.codechef.com/contests)
* [Codecombat](https://codecombat.com)
* [Codeeval](https://www.codeeval.com)
* [CodeFights](https://codefights.com)
* [Codeforces](http://codeforces.com/contests)
* [Codeground](https://www.codeground.org)
* [Coderbyte](https://coderbyte.com)
* [Codewars](http://www.codewars.com)
* [Codingame](https://www.codingame.com/start)
* [CSES Problem Set](https://cses.fi/problemset)
* [Dimik](https://dimikoj.com)
* [DMOJ](https://dmoj.ca)
* [E-olymp](https://www.e-olymp.com/en/)
* [Facebook Hackercup](https://www.facebook.com/hackercup)
* [Google Code Jam](https://codingcompetitions.withgoogle.com/codejam)
* [Google Kickstart](https://codingcompetitions.withgoogle.com/kickstart)
* [HackerEarth](https://www.hackerearth.com)
* [Hackerrank](https://www.hackerrank.com)
* [Internet Problem Solving Contest](http://ipsc.ksp.sk)
* [Just another Golf Coding](http://jagc.org)
* [Kattis](https://open.kattis.com)
* [LeetCode](https://leetcode.com)
* [LightOJ](https://lightoj.com)
* [Microcorruption](https://microcorruption.com/login)
* [oj.uz](https://oj.uz)
* [Sphere Online Judge](http://www.spoj.com/contests)
* [Techgig](https://www.techgig.com)
* [Topcoder](https://www.topcoder.com)
* [Toph](https://toph.co)


### Capture the flag

* [CTFlearn](https://ctflearn.com) (email address *requested*)
* [Google Ctf](https://capturetheflag.withgoogle.com) (email address *requested*)
* [Hacker101](https://ctf.hacker101.com) (email address *requested*)
* [Hackthebox](https://www.hackthebox.eu) (email address *requested*)
* [HackThisSite](https://www.hackthissite.org) (email address *requested*)
* [Overthewire Wargames fungame to practice CTF](https://overthewire.org/wargames/bandit)
* [Picoctf](https://picoctf.org/resources) (email address *requested*)
* [TryHackMe](https://tryhackme.com) (email address *requested*)


### Data science

* [AIcrowd](https://www.aicrowd.com)
* [CodaLab](https://competitions.codalab.org)
* [CrowdANALYTIX](https://www.crowdanalytix.com/community)
* [DrivenData](https://www.drivendata.org)
* [Kaggle](https://www.kaggle.com)
* [KDD Cup](https://www.kdd.org/kdd2019/kdd-cup)


### Information security

* [ångstromCTF](https://angstromctf.com)
* [CTFtime](https://ctftime.org)
* [Hacker101](https://ctf.hacker101.com)
* [InCTF](https://inctf.in)


### Problem Sets

* [500 Data structures and algorithms interview questions and their solutions in C++](https://www.quora.com/q/techiedelight/500-Data-Structures-and-Algorithms-interview-questions-and-their-solutions)
* [A2 Online Judge](https://a2oj.com/ps)
* [Advent Of Code](http://adventofcode.com)
* [Anarchy Golf](http://golf.shinh.org)
* [APL Practice Problems](https://problems.tryapl.org)
* [BaekJoon Online Judge](http://www.acmicpc.net)
* [beecrowd](https://www.beecrowd.com.br)
* [CareerCup](http://www.careercup.com)
* [CheckIO](http://www.checkio.org)
* [Codechef](https://www.codechef.com/problems/school)
* [Codedrills](https://codedrills.io/competitive)
* [Codeforces](http://codeforces.com/problemset)
* [Codility](https://codility.com/programmers/)
* [Coding Bat](http://codingbat.com/java)
* [Coding Interview Questions and answers for practice \| Python, Java & C++](https://www.codingninjas.com/codestudio/problems) - CodingNinjas
* [CSES Problem Set](https://cses.fi/problemset/)
* [Edabit](https://edabit.com)
* [Exercism](http://exercism.io)
* [Geeks For Geeks](https://practice.geeksforgeeks.org)
* [Google Code Jam - Practise](https://codingcompetitions.withgoogle.com/codejam/archive)
* [Hacker.org](http://www.hacker.org)
* [HackerEarth](https://www.hackerearth.com)
* [HDU Online Judge](http://acm.hdu.edu.cn)
* [Interactive Coding Challenge](https://github.com/donnemartin/interactive-coding-challenges)
* [InterviewBit](https://www.interviewbit.com)
* [Kattis](https://open.kattis.com)
* [Leetcode](https://leetcode.com)
* [Mathproblem of the Month - Bilkent University](http://www.fen.bilkent.edu.tr/~cvmath/prob-month.html)
* [PEG Judge](http://wcipeg.com)
* [PKU Online Judge](http://poj.org)
* [Ponder This!](https://www.research.ibm.com/haifa/ponderthis/index.shtml)
* [Practice Python](https://www.practicepython.org)
* [ProblemBook.NET](https://github.com/AndreyAkinshin/ProblemBook.NET)
* [Project Euler](https://projecteuler.net)
* [Python Practice Projects](http://pythonpracticeprojects.com)
* [Rosalind](http://rosalind.info/problems/locations/)
* [Sphere Online Judge](http://www.spoj.com/problems/classical)
* [TalentBuddy](http://www.talentbuddy.co/blog/)
* [Timus Online Judge](http://acm.timus.ru)
* [UVa Online Judge](https://uva.onlinejudge.org/index.php?Itemid=8&option=com_onlinejudge)
* [Школа программиста](https://acmp.ru)