Upload (Partially) Implemented BST

Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "bst-rs"
+version = "0.1.0"
+edition = "2021"
+authors = ["Goudham Suresh <sgoudham@gmail.com>"]
+description = "A simple BST implementation within Rust"
+license = "MIT"
+readme = "README.md"
+repository = "https://github.com/sgoudham/bst-rs"
+keywords = ["bst", "algorithms", "data-structures", "structure", "tree"]
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[lib]
+name = "bst_rs"
+
+[dependencies]

src/lib.rs

@@ -0,0 +1,654 @@
+use std::cmp::Ordering;
+use std::vec::IntoIter;
+
+#[derive(Debug)]
+pub struct BinarySearchTree<T: Ord> {
+    root: Child<T>,
+}
+
+type Child<T> = Option<Box<Node<T>>>;
+
+#[derive(Debug)]
+struct Node<T: Ord> {
+    value: T,
+    left: Child<T>,
+    right: Child<T>,
+}
+
+impl<T: Ord> Node<T> {
+    fn new(value: T) -> Self {
+        Node {
+            value,
+            left: None,
+            right: None,
+        }
+    }
+
+    fn insert(&mut self, value: T) {
+        match value.cmp(&self.value) {
+            Ordering::Equal => {}
+            Ordering::Less => match self.left {
+                None => self.left = Some(Box::from(Node::new(value))),
+                Some(ref mut node) => node.insert(value),
+            },
+            Ordering::Greater => match self.right {
+                None => self.right = Some(Box::from(Node::new(value))),
+                Some(ref mut node) => node.insert(value),
+            },
+        }
+    }
+
+    fn contains(&self, value: T) -> bool {
+        match value.cmp(&self.value) {
+            Ordering::Equal => true,
+            Ordering::Less => match self.left {
+                None => false,
+                Some(ref node) => node.contains(value),
+            },
+            Ordering::Greater => match self.right {
+                None => false,
+                Some(ref node) => node.contains(value),
+            },
+        }
+    }
+
+    fn retrieve(&self, value: T) -> Option<&T> {
+        match value.cmp(&self.value) {
+            Ordering::Equal => Some(&self.value),
+            Ordering::Less => match self.left {
+                None => None,
+                Some(ref node) => node.retrieve(value),
+            },
+            Ordering::Greater => match self.right {
+                None => None,
+                Some(ref node) => node.retrieve(value),
+            },
+        }
+    }
+
+    fn retrieve_as_mut(&mut self, value: T) -> Option<&mut T> {
+        match value.cmp(&self.value) {
+            Ordering::Equal => Some(&mut self.value),
+            Ordering::Less => match self.left {
+                None => None,
+                Some(ref mut node) => node.retrieve_as_mut(value),
+            },
+            Ordering::Greater => match self.right {
+                None => None,
+                Some(ref mut node) => node.retrieve_as_mut(value),
+            },
+        }
+    }
+
+    // https://users.rust-lang.org/t/binary-search-tree-node-removal-without-unsafe-code/56078
+    fn remove(mut root: &mut Child<T>, value: T) {
+        while let Some(ref mut node) = root {
+            match node.value.cmp(&value) {
+                Ordering::Less => root = &mut root.as_mut().unwrap().right,
+                Ordering::Greater => root = &mut root.as_mut().unwrap().left,
+                Ordering::Equal => match (node.left.as_mut(), node.right.as_mut()) {
+                    (None, None) => *root = None,
+                    (Some(_), None) => *root = node.left.take(),
+                    (None, Some(_)) => *root = node.right.take(),
+                    (Some(_), Some(_)) => {
+                        root.as_mut().unwrap().value = Self::extract_min(&mut node.right).unwrap()
+                    }
+                },
+            }
+        }
+    }
+
+    // https://users.rust-lang.org/t/binary-search-tree-node-removal-without-unsafe-code/56078
+    fn extract_min(node: &mut Child<T>) -> Option<T> {
+        let mut value = None;
+
+        if node.is_some() {
+            let mut current = node;
+
+            while current.as_ref().unwrap().left.is_some() {
+                current = &mut current.as_mut().unwrap().left;
+            }
+
+            let node = current.take().unwrap();
+            value = Some(node.value);
+            *current = node.right;
+        }
+
+        value
+    }
+
+    fn pre_order_traversal<'a>(node: &'a Child<T>, elements: &mut Vec<&'a T>) {
+        if let Some(ref node) = node {
+            elements.push(&node.value);
+            Self::pre_order_traversal(&node.left, elements);
+            Self::pre_order_traversal(&node.right, elements);
+        }
+    }
+
+    fn in_order_traversal<'a>(node: &'a Child<T>, elements: &mut Vec<&'a T>) {
+        if let Some(ref node) = node {
+            Self::in_order_traversal(&node.left, elements);
+            elements.push(&node.value);
+            Self::in_order_traversal(&node.right, elements);
+        }
+    }
+
+    fn post_order_traversal<'a>(node: &'a Child<T>, elements: &mut Vec<&'a T>) {
+        if let Some(ref node) = node {
+            Self::post_order_traversal(&node.left, elements);
+            Self::post_order_traversal(&node.right, elements);
+            elements.push(&node.value);
+        }
+    }
+
+    fn into_pre_order_traversal(node: Child<T>, elements: &mut Vec<T>) {
+        if let Some(node) = node {
+            elements.push(node.value);
+            Self::into_pre_order_traversal(node.left, elements);
+            Self::into_pre_order_traversal(node.right, elements);
+        }
+    }
+
+    fn into_in_order_traversal(node: Child<T>, elements: &mut Vec<T>) {
+        if let Some(node) = node {
+            Self::into_in_order_traversal(node.left, elements);
+            elements.push(node.value);
+            Self::into_in_order_traversal(node.right, elements);
+        }
+    }
+
+    fn into_post_order_traversal(node: Child<T>, elements: &mut Vec<T>) {
+        if let Some(node) = node {
+            Self::into_post_order_traversal(node.left, elements);
+            Self::into_post_order_traversal(node.right, elements);
+            elements.push(node.value);
+        }
+    }
+}
+
+impl<T: Ord + Copy> Node<T> {
+    fn pre_order_traversal_copy(node: &Child<T>, elements: &mut Vec<T>) {
+        if let Some(ref node) = node {
+            elements.push(node.value);
+            Self::pre_order_traversal_copy(&node.left, elements);
+            Self::pre_order_traversal_copy(&node.right, elements);
+        }
+    }
+
+    fn in_order_traversal_copy(node: &Child<T>, elements: &mut Vec<T>) {
+        if let Some(ref node) = node {
+            Self::in_order_traversal_copy(&node.left, elements);
+            elements.push(node.value);
+            Self::in_order_traversal_copy(&node.right, elements);
+        }
+    }
+
+    fn post_order_traversal_copy(node: &Child<T>, elements: &mut Vec<T>) {
+        if let Some(ref node) = node {
+            Self::post_order_traversal_copy(&node.left, elements);
+            Self::post_order_traversal_copy(&node.right, elements);
+            elements.push(node.value);
+        }
+    }
+}
+
+impl<T: Ord + Copy> BinarySearchTree<T> {
+    pub fn pre_order(&self) -> Vec<T> {
+        let mut elements: Vec<T> = Vec::new();
+        Node::pre_order_traversal_copy(&self.root, &mut elements);
+        elements
+    }
+
+    pub fn in_order(&self) -> Vec<T> {
+        let mut elements: Vec<T> = Vec::new();
+        Node::in_order_traversal_copy(&self.root, &mut elements);
+        elements
+    }
+
+    pub fn post_order(&self) -> Vec<T> {
+        let mut elements: Vec<T> = Vec::new();
+        Node::post_order_traversal_copy(&self.root, &mut elements);
+        elements
+    }
+}
+
+impl<T: Ord> BinarySearchTree<T> {
+    pub fn empty() -> Self {
+        Self { root: None }
+    }
+
+    pub fn new(value: T) -> Self {
+        Self {
+            root: Some(Box::from(Node::new(value))),
+        }
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.root.is_none()
+    }
+
+    pub fn insert(&mut self, value: T) {
+        match self.root {
+            None => self.root = Some(Box::from(Node::new(value))),
+            Some(ref mut node) => node.insert(value),
+        }
+    }
+
+    pub fn contains(&self, value: T) -> bool {
+        match self.root {
+            None => false,
+            Some(ref node) => node.contains(value),
+        }
+    }
+
+    pub fn remove(&mut self, value: T) {
+        Node::remove(&mut self.root, value);
+    }
+
+    pub fn retrieve(&self, value: T) -> Option<&T> {
+        match self.root {
+            None => None,
+            Some(ref node) => node.retrieve(value),
+        }
+    }
+
+    pub fn retrieve_as_mut(&mut self, value: T) -> Option<&mut T> {
+        match self.root {
+            None => None,
+            Some(ref mut node) => node.retrieve_as_mut(value),
+        }
+    }
+
+    pub fn pre_order_iter(&self) -> IntoIter<&T> {
+        let mut elements: Vec<&T> = Vec::new();
+        Node::pre_order_traversal(&self.root, &mut elements);
+        elements.into_iter()
+    }
+
+    pub fn in_order_iter(&self) -> IntoIter<&T> {
+        let mut elements: Vec<&T> = Vec::new();
+        Node::in_order_traversal(&self.root, &mut elements);
+        elements.into_iter()
+    }
+
+    pub fn post_order_iter(&self) -> IntoIter<&T> {
+        let mut elements: Vec<&T> = Vec::new();
+        Node::post_order_traversal(&self.root, &mut elements);
+        elements.into_iter()
+    }
+
+    pub fn into_pre_order_iter(self) -> IntoIter<T> {
+        let mut elements = Vec::new();
+        Node::into_pre_order_traversal(self.root, &mut elements);
+        elements.into_iter()
+    }
+
+    pub fn into_in_order_iter(self) -> IntoIter<T> {
+        let mut elements = Vec::new();
+        Node::into_in_order_traversal(self.root, &mut elements);
+        elements.into_iter()
+    }
+
+    pub fn into_post_order_iter(self) -> IntoIter<T> {
+        let mut elements = Vec::new();
+        Node::into_post_order_traversal(self.root, &mut elements);
+        elements.into_iter()
+    }
+}
+
+// impl<T: Ord> Drop for BST<T> {
+//     fn drop(&mut self) {
+//         todo!("I need help with this :sob: :sob:")
+//
+//         // let mut stack = vec![&self.root];
+//         // let mut out: Vec<&LinkNode<T>> = Vec::new();
+//         //
+//         // while !stack.is_empty() {
+//         //     let cur_node = stack.pop().unwrap();
+//         //     out.push(cur_node);
+//         //
+//         //     if let Some(node) = &cur_node.as_ref().unwrap().left {
+//         //         stack.push()
+//         //     }
+//         // }
+//     }
+// }
+
+#[cfg(test)]
+mod bst_test {
+    use super::BinarySearchTree;
+
+    #[test]
+    fn can_insert_element() {
+        let mut bst = BinarySearchTree::new(-1);
+
+        bst.insert(0);
+        bst.insert(1);
+        bst.insert(1);
+        bst.insert(2);
+
+        assert_eq!(bst.retrieve(-1), Some(&-1));
+        assert_eq!(bst.retrieve(0), Some(&0));
+        assert_eq!(bst.retrieve(1), Some(&1));
+        assert_eq!(bst.retrieve(2), Some(&2));
+    }
+
+    #[test]
+    fn check_if_bst_is_empty() {
+        let mut bst = BinarySearchTree::empty();
+        assert!(bst.is_empty());
+
+        bst.insert(1);
+        assert!(!bst.is_empty());
+    }
+
+    #[test]
+    fn check_element_exists() {
+        let mut bst = BinarySearchTree::empty();
+
+        bst.insert(1);
+        bst.insert(5);
+
+        assert!(!bst.contains(10));
+        assert!(bst.contains(1));
+        assert!(bst.contains(5));
+    }
+
+    #[test]
+    fn remove_root_element() {
+        let mut bst = BinarySearchTree::empty();
+        bst.insert(0);
+
+        bst.remove(0);
+
+        assert!(bst.is_empty())
+    }
+
+    #[test]
+    fn remove_leaf_node() {
+        let mut bst = BinarySearchTree::empty();
+        bst.insert(5);
+        bst.insert(4);
+        bst.insert(6);
+        bst.insert(7);
+
+        bst.remove(7);
+
+        assert!(!bst.contains(7));
+        assert_eq!(bst.in_order(), vec![4, 5, 6])
+    }
+
+    #[test]
+    fn remove_single_right_node_with_children() {
+        let mut bst = BinarySearchTree::empty();
+        bst.insert(5);
+        bst.insert(4);
+        bst.insert(6);
+        bst.insert(7);
+        bst.insert(8);
+
+        bst.remove(6);
+
+        assert!(!bst.contains(6));
+        assert_eq!(bst.in_order(), vec![4, 5, 7, 8])
+    }
+
+    #[test]
+    fn remove_single_left_node_with_children() {
+        let mut bst = BinarySearchTree::empty();
+        bst.insert(5);
+        bst.insert(4);
+        bst.insert(6);
+        bst.insert(3);
+        bst.insert(2);
+
+        bst.remove(4);
+
+        assert!(!bst.contains(4));
+        assert_eq!(bst.in_order(), vec![2, 3, 5, 6])
+    }
+
+    #[test]
+    fn remove_node_with_two_children() {
+        let mut bst = BinarySearchTree::empty();
+        bst.insert(10);
+        bst.insert(5);
+        bst.insert(8);
+        bst.insert(3);
+        bst.insert(15);
+
+        bst.remove(5);
+
+        assert!(!bst.contains(5));
+        assert_eq!(bst.in_order(), vec![3, 8, 10, 15])
+    }
+
+    #[test]
+    fn does_not_fail_when_removing_non_existing_element() {
+        let mut bst = BinarySearchTree::empty();
+        bst.insert(10);
+        bst.insert(5);
+        bst.insert(8);
+        bst.insert(3);
+        bst.insert(15);
+
+        bst.remove(20);
+
+        assert!(!bst.contains(20));
+        assert_eq!(bst.in_order(), vec![3, 5, 8, 10, 15])
+    }
+
+    #[test]
+    fn retrieve_element() {
+        let mut bst = BinarySearchTree::empty();
+        bst.insert(5);
+        bst.insert(10);
+
+        let retrieved_value = bst.retrieve(5);
+        let invalid_value = bst.retrieve(15);
+
+        assert_eq!(retrieved_value, Some(&5));
+        assert_eq!(invalid_value, None);
+    }
+
+    #[test]
+    fn retrieve_element_as_mut_and_modify_bst() {
+        let mut bst = BinarySearchTree::empty();
+        bst.insert(10);
+        bst.insert(5);
+
+        let _retrieved_value_as_mut: &mut i32 = bst.retrieve_as_mut(5).unwrap();
+        *_retrieved_value_as_mut = 2;
+
+        assert!(bst.contains(10));
+        assert!(bst.contains(2));
+        assert!(!bst.contains(5));
+    }
+
+    #[test]
+    fn pre_order_traversal() {
+        let mut bst = BinarySearchTree::empty();
+        bst.insert(3);
+        bst.insert(4);
+        bst.insert(5);
+        bst.insert(1);
+        bst.insert(2);
+
+        let mut pre_order_iter = bst.pre_order_iter();
+
+        assert_eq!(pre_order_iter.next(), Some(&3));
+        assert_eq!(pre_order_iter.next(), Some(&1));
+        assert_eq!(pre_order_iter.next(), Some(&2));
+        assert_eq!(pre_order_iter.next(), Some(&4));
+        assert_eq!(pre_order_iter.next(), Some(&5));
+        assert_eq!(pre_order_iter.next(), None);
+
+        bst.insert(10);
+
+        let mut another_pre_order_iter = bst.pre_order_iter();
+
+        assert_eq!(another_pre_order_iter.next(), Some(&3));
+        assert_eq!(another_pre_order_iter.next(), Some(&1));
+        assert_eq!(another_pre_order_iter.next(), Some(&2));
+        assert_eq!(another_pre_order_iter.next(), Some(&4));
+        assert_eq!(another_pre_order_iter.next(), Some(&5));
+        assert_eq!(another_pre_order_iter.next(), Some(&10));
+        assert_eq!(another_pre_order_iter.next(), None);
+    }
+
+    #[test]
+    fn in_order_traversal() {
+        let mut bst = BinarySearchTree::empty();
+        bst.insert(3);
+        bst.insert(4);
+        bst.insert(5);
+        bst.insert(1);
+        bst.insert(2);
+
+        let mut in_order_iter = bst.in_order_iter();
+
+        assert_eq!(in_order_iter.next(), Some(&1));
+        assert_eq!(in_order_iter.next(), Some(&2));
+        assert_eq!(in_order_iter.next(), Some(&3));
+        assert_eq!(in_order_iter.next(), Some(&4));
+        assert_eq!(in_order_iter.next(), Some(&5));
+        assert_eq!(in_order_iter.next(), None);
+
+        bst.insert(6);
+
+        let mut another_in_order_iter = bst.in_order_iter();
+
+        assert_eq!(another_in_order_iter.next(), Some(&1));
+        assert_eq!(another_in_order_iter.next(), Some(&2));
+        assert_eq!(another_in_order_iter.next(), Some(&3));
+        assert_eq!(another_in_order_iter.next(), Some(&4));
+        assert_eq!(another_in_order_iter.next(), Some(&5));
+        assert_eq!(another_in_order_iter.next(), Some(&6));
+        assert_eq!(another_in_order_iter.next(), None);
+    }
+
+    #[test]
+    fn post_order_traversal() {
+        let mut bst = BinarySearchTree::empty();
+        bst.insert(3);
+        bst.insert(4);
+        bst.insert(5);
+        bst.insert(1);
+        bst.insert(2);
+
+        let mut post_order_iter = bst.post_order_iter();
+        println!("{:?}", bst);
+
+        assert_eq!(post_order_iter.next(), Some(&2));
+        assert_eq!(post_order_iter.next(), Some(&1));
+        assert_eq!(post_order_iter.next(), Some(&5));
+        assert_eq!(post_order_iter.next(), Some(&4));
+        assert_eq!(post_order_iter.next(), Some(&3));
+        assert_eq!(post_order_iter.next(), None);
+
+        bst.insert(10);
+
+        let mut another_post_order_iter = bst.post_order_iter();
+
+        assert_eq!(another_post_order_iter.next(), Some(&2));
+        assert_eq!(another_post_order_iter.next(), Some(&1));
+        assert_eq!(another_post_order_iter.next(), Some(&10));
+        assert_eq!(another_post_order_iter.next(), Some(&5));
+        assert_eq!(another_post_order_iter.next(), Some(&4));
+        assert_eq!(another_post_order_iter.next(), Some(&3));
+        assert_eq!(another_post_order_iter.next(), None);
+    }
+
+    #[test]
+    fn into_pre_order_traversal() {
+        let mut bst = BinarySearchTree::empty();
+        bst.insert(3);
+        bst.insert(4);
+        bst.insert(5);
+        bst.insert(1);
+        bst.insert(2);
+
+        let mut pre_order_iter = bst.into_pre_order_iter();
+
+        assert_eq!(pre_order_iter.next(), Some(3));
+        assert_eq!(pre_order_iter.next(), Some(1));
+        assert_eq!(pre_order_iter.next(), Some(2));
+        assert_eq!(pre_order_iter.next(), Some(4));
+        assert_eq!(pre_order_iter.next(), Some(5));
+        assert_eq!(pre_order_iter.next(), None);
+    }
+
+    #[test]
+    fn into_in_order_traversal() {
+        let mut bst = BinarySearchTree::empty();
+        bst.insert(3);
+        bst.insert(4);
+        bst.insert(5);
+        bst.insert(1);
+        bst.insert(2);
+
+        let mut in_order_iter = bst.into_in_order_iter();
+
+        assert_eq!(in_order_iter.next(), Some(1));
+        assert_eq!(in_order_iter.next(), Some(2));
+        assert_eq!(in_order_iter.next(), Some(3));
+        assert_eq!(in_order_iter.next(), Some(4));
+        assert_eq!(in_order_iter.next(), Some(5));
+        assert_eq!(in_order_iter.next(), None);
+    }
+
+    #[test]
+    fn into_post_order_traversal() {
+        let mut bst = BinarySearchTree::empty();
+        bst.insert(3);
+        bst.insert(4);
+        bst.insert(5);
+        bst.insert(1);
+        bst.insert(2);
+
+        let mut post_order_traversal = bst.into_post_order_iter();
+
+        assert_eq!(post_order_traversal.next(), Some(2));
+        assert_eq!(post_order_traversal.next(), Some(1));
+        assert_eq!(post_order_traversal.next(), Some(5));
+        assert_eq!(post_order_traversal.next(), Some(4));
+        assert_eq!(post_order_traversal.next(), Some(3));
+        assert_eq!(post_order_traversal.next(), None);
+    }
+
+    #[test]
+    fn pre_order_traversal_copy() {
+        let mut bst = BinarySearchTree::empty();
+        bst.insert(3);
+        bst.insert(4);
+        bst.insert(5);
+        bst.insert(1);
+        bst.insert(2);
+
+        assert_eq!(bst.pre_order(), vec![3, 1, 2, 4, 5]);
+    }
+
+    #[test]
+    fn in_order_traversal_copy() {
+        let mut bst = BinarySearchTree::empty();
+        bst.insert(3);
+        bst.insert(4);
+        bst.insert(5);
+        bst.insert(1);
+        bst.insert(2);
+
+        assert_eq!(bst.in_order(), vec![1, 2, 3, 4, 5]);
+    }
+
+    #[test]
+    fn post_order_traversal_copy() {
+        let mut bst = BinarySearchTree::empty();
+        bst.insert(3);
+        bst.insert(4);
+        bst.insert(5);
+        bst.insert(1);
+        bst.insert(2);
+
+        assert_eq!(bst.post_order(), vec![2, 1, 5, 4, 3]);
+    }
+}