leetcode-bt

binary_tree_traversal.py

"""
Given a bst
           5
          / \
         3   7
        / \  /
       1  4 6
pre-order: 5->  3    ->     7   ==> 5->3->1->4->7->6
              /  \         /
              1   4       6
              
post-order:  3     ->  7 -> 5 ==> 1->4->3->6->7->5
            / \       /
           1   4     6

in-order:  3    -> 5 ->   7 ==> 1->3->4->5->6->7
          / \            /
         1   4          6
"""
def preorder(root):
    """root -> left subtree -> right subtree"""
    if not root:
        return
    print (root.val)
    preorder(root.left)
    preorder(root.right)

def postorder(root):
    """left subtree -> right subtree -> root"""
    if not root:
        return
    postorder(root.left)
    postorder(root.right)
    print (root.val)
    
def inorder(root):
    """left subtree -> root -> right subtree"""
    if not root:
        return
    inorder(root.left)
    print (root.val)
    inorder(root.right)