Data structures are amongst the most fundamental ingredients in the recipe for efficient algorithms and good software design. Knowledge of how to create and design excellent data structures is an essential skill required in becoming an exemplary programmer. The goal of this repository is to provide a complete and thorough explanation of the most common data structures.

• Balanced Trees
  • Avl Tree (recursive)
  • Avl Tree (recursive, mildly optimized)
  • Red Black Tree(recursive)
• Binary Search Tree
• Bloom Filter
• Dynamic Array
  • Dynamic array (integer only, fast)
  • Dynamic array (generic)
• Fenwick Tree
  • Fenwick Tree (range query, point updates)
  • Fenwick Tree (range update, point query)
• Set
• Hashtable
  • Hashtable (double hashing)
  • Hashtable (linear probing)
  • Hashtable (quadratic probing)
  • Hashtable (separate chaining)
• Linked List
• Priority Queue
  • Min Binary Heap
  • Min Indexed Binary Heap (sorted key-value pairs, similar to hash-table)
  • Min D-Heap
  • Min Indexed D-Heap (sorted key-value pairs, similar to hash-table)
• Quad Tree [WIP]
• Queue
  • Queue (integer only, fixed size, fast)
  • Queue (linked list, generic)
• Segment Tree
  • Segment tree (array based, compact)
  • Segment tree (pointer implementation)
• Skip List [UNTESTED]
• Stack
  • Stack (integer only, fixed size, fast)
  • Stack (linked list, generic)
• Suffix Array
  • Suffix Array (O(n²logn) construction)
  • Suffix Array (O(nlog²(n)) construction)
  • Suffix Array (O(nlog(n)) construction)
• Trie
• Union Find

This repository is contribution friendly 😃. If you're a data structures enthusiast (like me!) and want to add or improve a data structure your contribution is welcome! Please be sure to include tests 😘

This project uses Gradle as a build system and for testing. To get started install the gradle command-line tool and run the build command to make sure you don't get any errors:

data-structures$ gradle build

The procedure to add a new data structure named Foo is the following:

1. Create a new folder called Foo in com/williamfiset/datastrutures/Foo
2. Add the data structure implementation for Foo in com/williamfiset/datastrutures/Foo/Foo.java
3. Add tests for Foo in javatests/com/williamfiset/datastrutures/Foo/FooTest.java
4. Edit the build.gradle file and add Foo to the project.
5. Add tests for your data structure 😘
6. Send pull request for review 😮

This repository places a large emphasis on good testing practice to ensure that published data structures are bug free and high quality. Testing is done using a combinations of frameworks including: JUnit, Mockito and the Google Truth framework, but mostly JUnit.

When developing you likely do not want to run all tests but only a subset of them. For example, if you want to run the LinkedListTest.java file under javatests/com/williamfiset/datastructures/linkedlist/LinkedListTest.java you can execute:

data-structures$ gradle test --tests "javatests.com.williamfiset.datastructures.linkedlist.LinkedListTest"

Sometimes there are many test files for one data structure. One example is the 🌲FenwickTree🌲 which currently has two test files: FenwickTreeRangeQueryPointUpdateTest.java and FenwickTreeRangeUpdatePointQueryTest.java, in which case you can specify a glob expression to capture all the appropriate test files:

gradle test --tests "javatests.com.williamfiset.datastructures.fenwicktree.FenwickTree*Test"

This repository is released under the MIT license. In short, this means you are free to use this software in any personal, open-source or commercial projects. Attribution is optional but appreciated.