From c0dc9e794e121a9171ab05acb727437777cbfc7f Mon Sep 17 00:00:00 2001
From: Jesse Brault <jbrault@mac.com>
Date: Fri, 22 Nov 2024 15:41:29 -0600
Subject: [PATCH] Add BST and differentiate Stack.

---
 src/bst.rs   | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/main.rs  | 73 +++++++++++++++++--------------------------------
 src/stack.rs | 43 +++++++++++++++++++++++++++++
 3 files changed, 143 insertions(+), 49 deletions(-)
 create mode 100644 src/bst.rs
 create mode 100644 src/stack.rs

diff --git a/src/bst.rs b/src/bst.rs
new file mode 100644
index 0000000..33fc57a
--- /dev/null
+++ b/src/bst.rs
@@ -0,0 +1,76 @@
+use std::cmp::Ordering::*;
+
+#[derive(Debug)]
+pub struct BinarySearchTree<T: Ord> {
+    root: Option<Box<Node<T>>>,
+}
+
+#[derive(Debug)]
+struct Node<T> {
+    data: T,
+    left: Option<Box<Node<T>>>,
+    right: Option<Box<Node<T>>>,
+}
+
+impl<T: Ord> BinarySearchTree<T> {
+    pub fn new() -> BinarySearchTree<T> {
+        BinarySearchTree { root: None }
+    }
+
+    pub fn insert(&mut self, data: T) {
+        match self.root.take() {
+            None => {
+                self.root = Some(Box::new(Node {
+                    data,
+                    left: None,
+                    right: None,
+                }))
+            }
+            Some(mut root) => {
+                root.insert_child(data);
+                self.root = Some(root);
+            }
+        }
+    }
+
+    pub fn find(&mut self, data: T) -> Option<T> {
+        self.root.take().map(|mut root| root.find(data))?
+    }
+}
+
+impl<T: Ord> Node<T> {
+    fn new(data: T) -> Self {
+        Node {
+            data,
+            left: None,
+            right: None,
+        }
+    }
+
+    fn insert_child(&mut self, data: T) {
+        match self.data.cmp(&data) {
+            Less => match self.right.take() {
+                None => self.right = Some(Box::new(Node::new(data))),
+                Some(mut right) => {
+                    right.insert_child(data);
+                    self.right = Some(right);
+                }
+            },
+            Equal | Greater => match self.left.take() {
+                None => self.left = Some(Box::new(Node::new(data))),
+                Some(mut left) => {
+                    left.insert_child(data);
+                    self.left = Some(left);
+                }
+            },
+        }
+    }
+
+    fn find(&mut self, data: T) -> Option<T> {
+        match self.data.cmp(&data) {
+            Less => self.right.take().map(|mut right| right.find(data))?,
+            Equal => Some(data),
+            Greater => self.left.take().map(|mut left| left.find(data))?,
+        }
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index 214b8fb..2141259 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,9 @@
+mod bst;
+mod stack;
+
+use bst::BinarySearchTree;
+use stack::Stack;
+
 struct Greeter {
     greeting: &'static str,
 }
@@ -12,59 +18,28 @@ impl Greeter {
     }
 }
 
-struct LinkedList<T> {
-    head: Link<T>,
-}
-
-enum Link<T> {
-    Empty,
-    More(Box<Node<T>>),
-}
-
-struct Node<T> {
-    data: T,
-    next: Link<T>,
-}
-
-impl<T> LinkedList<T> {
-    fn new() -> Self {
-        LinkedList { head: Link::Empty }
-    }
-
-    fn push(&mut self, data: T) {
-        self.head = Link::More(Box::new(Node {
-            data,
-            next: std::mem::replace(&mut self.head, Link::Empty),
-        }));
-    }
-
-    fn pop(&mut self) -> Option<T> {
-        match std::mem::replace(&mut self.head, Link::Empty) {
-            Link::Empty => None,
-            Link::More(node) => {
-                self.head = node.next;
-                Some(node.data)
-            }
-        }
-    }
-}
-
-impl<T> Iterator for LinkedList<T> {
-    type Item = T;
-    fn next(&mut self) -> Option<Self::Item> {
-        self.pop()
-    }
-}
-
 fn main() {
     Greeter::new("Hello, Jesse!").greet();
 
-    let mut my_linked_list = LinkedList::new();
-    my_linked_list.push(Greeter::new("Hello"));
-    my_linked_list.push(Greeter::new("Beautiful"));
-    my_linked_list.push(Greeter::new("World"));
+    let mut my_stack = Stack::new();
+    my_stack.push(Greeter::new("Hello"));
+    my_stack.push(Greeter::new("Beautiful"));
+    my_stack.push(Greeter::new("World"));
 
-    for greeter in my_linked_list {
+    for greeter in my_stack {
         greeter.greet();
     }
+
+    // BST
+
+    let mut bst = BinarySearchTree::new();
+    bst.insert(1);
+    bst.insert(2);
+    bst.insert(3);
+
+    println!("{:?}", bst);
+
+    bst.insert(0);
+    println!("{:?}", bst);
+    println!("find result: {:?}", bst.find(0));
 }
diff --git a/src/stack.rs b/src/stack.rs
new file mode 100644
index 0000000..daa49fd
--- /dev/null
+++ b/src/stack.rs
@@ -0,0 +1,43 @@
+pub struct Stack<T> {
+    head: Link<T>,
+}
+
+enum Link<T> {
+    Empty,
+    More(Box<Node<T>>),
+}
+
+struct Node<T> {
+    data: T,
+    next: Link<T>,
+}
+
+impl<T> Stack<T> {
+    pub fn new() -> Self {
+        Stack { head: Link::Empty }
+    }
+
+    pub fn push(&mut self, data: T) {
+        self.head = Link::More(Box::new(Node {
+            data,
+            next: std::mem::replace(&mut self.head, Link::Empty),
+        }));
+    }
+
+    pub fn pop(&mut self) -> Option<T> {
+        match std::mem::replace(&mut self.head, Link::Empty) {
+            Link::Empty => None,
+            Link::More(node) => {
+                self.head = node.next;
+                Some(node.data)
+            }
+        }
+    }
+}
+
+impl<T> Iterator for Stack<T> {
+    type Item = T;
+    fn next(&mut self) -> Option<Self::Item> {
+        self.pop()
+    }
+}