Maximum Depth of Binary Tree

Tree BFS

Problem

Given the root of a binary tree, return its maximum depth.

A binary tree's maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

Solution

from collections import deque
class Solution:
    def maxDepth(self, root: TreeNode) -> int:
        if root is None:
            return 0
        
        depthCount = 0
        queue = deque()
        queue.append(root)
        
        while queue:
            depthCount+=1
            levelSize = len(queue)
            
            for _ in range(levelSize):
                currentNode = queue.popleft()
                
                if currentNode.left:
                    queue.append(currentNode.left)
                if currentNode.right:
                    queue.append(currentNode.right)
        return depthCount
        
#Time: O(n)
#Space: O(n)