Recursive & Iterative Binary Search Tree Implementations within Rust

Last update: Oct 1, 2022

Overview

bst-rs

Recursive & Iterative Binary Search Tree Implementations within Rust

Personal Goals
About
Quick Start
License
Contributing
Inspiration

About

This crate contains Recursive & Iterative Binary Search Tree Implementations. All common operations are included along with common traversal iterators.

All elements within the Binary Search Trees must implement the Ord trait.

It is also important to note that RecursiveBST is more likely to blow the stack. For more information on why that is the case, please have a look at The Story of Tail Call Optimizations in Rust.

Personal Goals

I have made this library with the personal goals of learning and solidifying concepts such as ownership, borrowing , generics and lifetimes. I cannot promise that the implementations are particularly efficient, or if they are, it was not at the forefront of my mind.

That being said, there are some areas I would love to improve/include:

Write Rust more idiomatically.
Implement a pretty_print() function to display the binary search trees nicely.
Implementing the Drop trait for iterative node cleanup.
Pre-allocating space on the heap for nodes to reduce inefficiency of inserts.

I'm more than happy to accept (and encourage) contributions if anyone is kind enough to do so. (Please look at CONTRIBUTING!)

Quick Start

use bst_rs::{BinarySearchTree, IterativeBST, RecursiveBST};

// Create new empty binary search trees
let mut iterative_bst = IterativeBST::new();
assert!(iterative_bst.is_empty());

let mut recursive_bst = RecursiveBST::new();
assert!(recursive_bst.is_empty());

// Insert elements (no duplicates are allowed)
iterative_bst.insert(10);
iterative_bst.insert(10);   // Element is not inserted
iterative_bst.insert(5);
iterative_bst.insert(2);
iterative_bst.insert(15);
iterative_bst.insert(25);

assert_eq!(iterative_bst.size(), 5);
recursive_bst.insert(10);
recursive_bst.insert(10);   // Element is not inserted
recursive_bst.insert(5);
recursive_bst.insert(2);
recursive_bst.insert(15);
recursive_bst.insert(25);
assert_eq!(recursive_bst.size(), 5);

// Check if element exists
assert!(iterative_bst.contains(&5));    // true
assert!(!iterative_bst.contains(&0));   // false
assert!(recursive_bst.contains(&5));    // true
assert!(!recursive_bst.contains(&0));   // false

// Remove elements
iterative_bst.remove(&10);
iterative_bst.remove(&50); // No change to tree as element does not exist
assert_eq!(iterative_bst.size(), 4);

recursive_bst.remove(&10);
recursive_bst.remove(&50); // No change to tree as element does not exist
assert_eq!(recursive_bst.size(), 4);

// View pre-order, in-order and post-order traversals
assert_eq!(iterative_bst.pre_order_vec(), vec![&15, &5, &2, &25]);
assert_eq!(iterative_bst.in_order_vec(), vec![&2, &5, &15, &25]);
assert_eq!(iterative_bst.post_order_vec(), vec![&2, &5, &25, &15]);

assert_eq!(recursive_bst.pre_order_vec(), vec![&15, &5, &2, &25]);
assert_eq!(recursive_bst.in_order_vec(), vec![&2, &5, &15, &25]);
assert_eq!(recursive_bst.post_order_vec(), vec![&2, &5, &25, &15]);

// Compare equality of trees
assert_eq!(iterative_bst.sorted_vec(), recursive_bst.sorted_vec());
assert_ne!(iterative_bst, IterativeBST::new());
assert_ne!(recursive_bst, RecursiveBST::new());

License

MIT License

Contributing

Please read the CONTRIBUTING.md before contributing! (Thank you!)

Inspiration

The book Learn Rust With Entirely Too Many Linked Lists inspired me to try and implement a Binary Search Trees within the language. I had also been wanting to create my first library for other crates to use.

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Comments

Improve documentation

This change aims to improve on the grammar in the comments. I also adjusted the Personal Goals link in the README to match the order in the detailed section.

These are not very critical changes. As a newbie to Rust,the goal for me here is to get familiar with the project as I find it particularly interesting :)

opened by nassersaazi 1
[v0.1.1] -> Add bst![] macro defaulting to IterativeBST
Motivation

Users can currently only use IterativeBST & RecursiveBST structs directly for creating BinarySearchTrees. We should streamline this process by implementing a declarative macro that can instantiate the tree for them that defaults to the IterativeBST implementation.

E.G Given the user wants to represent the following tree:

graph TB; A((8))-->B((3)) A-->C((10)) B-->D((1)) B-->E((6)) C-->F((9)) C-->G((15))

The code could look like:

let mut bst = bst![8, 10, 9, 15, 3, 6, 1];

What We Need To Do

Add bst![] macro that defaults to the IterativeBST implementation.
enhancement good first issue
opened by sgoudham 0
[v0.1.1] -> Add retrieval methods for Predecessor & Successor
Context

Common operations surrounding BST's are retrieving Predecessor & Successor Successors. The definitions of both terms are as follows:

Successor

The Successor can be thought of as the smallest value greater than the value of the given node.

E.G. Given a tree that looks like:

graph TB; A((8))-->B((3)) A-->C((10)) B-->D((1)) B-->E((6)) C-->F((9)) C-->G((14)) E-->H((4)) E-->I((7))

The Successor of 3 is 4.

Predecessor

The Predecessor can be thought of as the greatest value less than the value of the given node.

E.G Given a tree that looks like:

graph TB; A((8))-->B((3)) A-->C((10)) B-->D((1)) B-->E((6)) C-->F((9)) C-->G((14)) E-->H((4)) E-->I((7))

The Predecessor of 8 is 7.

What We Need To Do

Successor & Predecessor retrieval methods should implemented as part of the BinarySearchTree trait and implemented within RecursiveBST & IterativeBST
enhancement good first issue
opened by sgoudham 0