leetcode_104_solution_2.py

# Iterative DFS solution using a stack
def maxDepth(self, root: Optional[TreeNode]) -> int:
    if not root:
        return 0
        
    stack = [(root, 1)] # (Node, depth of Node)
    maxDepth = 1
    
    while stack:
        node, depth = stack.pop()
        maxDepth = max(maxDepth, depth)
        
        if node.left:
            stack.append((node.left, depth+1))
        if node.right:
            stack.append((node.right, depth+1))
    return maxDepth