BST Insert - Rust DSA

Insert values into a binary search tree by comparing at each node.

Algorithm

The canonical tree is 4(2(1,3),6(5,7)), so this Rust DSA implementation can be compared directly with the rest of the DSA track.

Basic Implementation

basic.rs

use std::collections::VecDeque;
struct Node { value: i32, left: Option<Box<Node>>, right: Option<Box<Node>> }
impl Node {
    fn new(value: i32) -> Self { Self { value, left: None, right: None } }
    fn with(value: i32, left: Node, right: Node) -> Self {
        Self { value, left: Some(Box::new(left)), right: Some(Box::new(right)) }
    }
}
fn render(node: &Option<Box<Node>>) -> String {
    match node {
        None => "_".to_string(),
        Some(n) => {
            if n.left.is_none() && n.right.is_none() { n.value.to_string() }
            else { format!("{}({},{})", n.value, render(&n.left), render(&n.right)) }
        }
    }
}
fn sample_tree() -> Option<Box<Node>> {
    Some(Box::new(Node::with(4, Node::with(2, Node::new(1), Node::new(3)), Node::with(6, Node::new(5), Node::new(7)))))
}
fn list_string(values: &[i32]) -> String {
    format!("[{}]", values.iter().map(|v| v.to_string()).collect::<Vec<_>>().join(", "))
}
fn insert(root: &mut Option<Box<Node>>, value: i32) { match root { None => *root = Some(Box::new(Node::new(value))), Some(node) => if value < node.value { insert(&mut node.left, value) } else { insert(&mut node.right, value) } } }
fn main() { let mut root = None; for value in [4, 2, 6, 1, 3, 5, 7] { insert(&mut root, value); } println!("{}", render(&root)); }

Complexity

Time: O(h) per insert
Space: O(n)

Implementation notes

Render tree structure explicitly instead of printing node objects.
The replay highlights the node, traversal state, queue, path, or search cursor that changes at each step.

binary search tree Values smaller than a node go left; larger values go right.