Algorithms-and-Data-Structures/Rust-Trees-With-Arrays/src/main.rs

fn main() {
    part_b();
}

/*```Pseudocode
let left: int[]   = [1,  3, -1, -1, 5, -1, -1]
let right: int[]  = [2,  4, -1, -1, 6, -1, -1]
let values: int[] = [31, 16, 45, 7, 24, 19, 29]
```*/

fn part_b() {
    let left: Vec<Option<usize>> = vec![Some(1), Some(3), None, None, Some(5), None, None];
    let right: Vec<Option<usize>> = vec![Some(2),  Some(4), None, None, Some(6), None, None];
    let values: Vec<usize> = vec![31, 16, 45, 7, 24, 19, 29];

    println!("POST ORDER");
    post_order(&left, &right, &values, 0);

    println!("BREADTH FIRST CHEATING");
    breadth_first_cheating(&values);

    println!("BREADTH FIRST");
    breadth_first(&left, &right, &values, 0);
}

/*```Pseudocode
fn post_order(left, right, values, node) {
    if (left[node] != -1) {
        post_order(left, right, values, left[node])
    }

    if (right[node] != -1) {
        post_order(left, right, values, right[node])
    }

    print(values[node])
}
```*/

fn post_order(left: &Vec<Option<usize>>, right: &Vec<Option<usize>>, values: &Vec<usize>, node: usize) {
    match left[node] {
        Some(new_node) => post_order(left, right, values, new_node),
        None => {},
    }

    match right[node] {
        Some(new_node) => post_order(left, right, values, new_node),
        None => {},
    }

    println!("{}", values[node])
}

/*```Pseudocode
for i in 0..values.len {
    print(values[i])
}
```*/

fn breadth_first_cheating(values: &Vec<usize>) {
   for value in values {
    println!("{value}");
   }
}

/*```Pseudocode
fn breadth_first(left, right, values, root) {
    queue = new Queue
    queue.enqueue(root)

    while (queue.isNotEmpty()) {
        node = queue.dequeue()
        print(values[node])

        if (left[node] != -1) {
            queue.enqueue(left[node])
        }

        if (right[node] != -1) {
            queue.enqueue(right[node])
        }
    }
}
```*/

fn breadth_first(left: &Vec<Option<usize>>, right: &Vec<Option<usize>>, values: &Vec<usize>, root: usize) {
    let mut queue = std::collections::VecDeque::new();
    queue.push_back(root);

    while let Some(node) = queue.pop_front() {
        println!("{}", values[node]);

        if let Some(left_child) = left[node] {
            queue.push_back(left_child);
        }

        if let Some(right_child) = right[node] {
            queue.push_back(right_child);
        }
    }
}