LeetCodeProblems/MaximumDepthInBinaryTree.py at main · Khalidur-sujon/LeetCodeProblems · GitHub

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................. DFS Recursion......................

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def maxDepth(self, root: Optional[TreeNode]) -> int:
        if not root:
            return 0
        return 1 + max(self.maxDepth(root.left), self.maxDepth(root.right))


...........Iterative BFS .................

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def maxDepth(self, root: Optional[TreeNode]) -> int:
        if not root:
            return 0

        level = 0
        q = deque([root])
        while q:
            for i in range(len(q)):
                CurrNode = q.popleft()
                if CurrNode.left:
                    q.append(CurrNode.left)
                if CurrNode.right:
                    q.append(CurrNode.right)
            level += 1
        return level

........................... Iterative DFS............

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def maxDepth(self, root: Optional[TreeNode]) -> int:
        if not root:
            return 0

        stack = [[root, 1]]
        res = 1
        while stack:
            node, depth = stack.pop()
            if node:
                res = max(res, depth)
                stack.append((node.left, depth + 1))
                stack.append((node.right, depth + 1))

        return res