Binary tree and its traversal method!

binary tree

What is a binary tree?

Each node in the tree can only have at most two child nodes. In JavaScript, Object is generally used to simulate a binary tree.

common operation

• preorder traversal
• Inorder traversal
• post order traversal

preorder traversal

root or so.

Mantra:

1. visit the root node
2. Preorder traversal of the left subtree of the root node
3. Preorder traversal of the right subtree of the root node
   

Implemented recursively

function preorder(root) {
    
    
    if (!root) return

    console.log(root.val)
    preorder(root.left)
    preorder(root.right)
}

Implemented iteratively

function preorder(root) {
    
    
    if (!root) return

    const stack = [root]

    while (stack.length) {
    
    
        const n = stack.pop()

        console.log(n)
        if (n.right) stack.push(n.right)
        if (n.left) stack.push(n.left)
    }
}

Inorder traversal

Left and right.

Mantra:

1. Inorder traversal of the left subtree of the root node
2. visit the root node
3. Inorder traversal of the right subtree of the root node

Implemented recursively

function inorder(root) {
    
    
    if (!root) return

    inorder(root.left)
    console.log(root.val)
    inorder(root.right)
}

Implemented iteratively

function inorder(root) {
    
    
    if (!root) return

    const stack = [root]

    while (stack.length) {
    
    
        const n = stack.pop()

        console.log(n)
        if (n.right) stack.push(n.right)
        if (n.left) stack.push(n.left)
    }
}

post order traversal

left and right roots.

Mantra:

1. Post-order traversal of the left subtree of the root node
2. Post-order traversal of the right subtree of the root node
3. visit the root node

Implemented recursively

function postorder(root) {
    
    
    if (!root) return

    postorder(root.left)
    postorder(root.right)
    console.log(root.val)
}

Implemented iteratively

function postorder(root) {
    
    
    if (!root) return

    const outputStack = []
    const stack = [root]

    while (stack.length) {
    
    
        const n = stack.pop()

        outputStack.push(n)
        if (n.left) stack.push(n.left)
        if (n.right) stack.push(n.right)
    }

    while (outputStack.length) {
    
    
        const n = outputStack.pop()
        console.log(n.val)
    }
}

Original Link: Vegetable Garden Front End