Maximum Depth of Binary Tree — DFS and BFS Approaches

// C
int maxDepth(struct TreeNode* root) {
    if (!root) return 0;
    int l = maxDepth(root->left), r = maxDepth(root->right);
    return 1 + (l>r?l:r);
}

// C++
int maxDepth(TreeNode* root) {
    if (!root) return 0;
    return 1 + max(maxDepth(root->left), maxDepth(root->right));
}

// Java
public int maxDepth(TreeNode root) {
    if (root == null) return 0;
    return 1 + Math.max(maxDepth(root.left), maxDepth(root.right));
}

# Python — recursive
def maxDepth(root):
    if not root: return 0
    return 1 + max(maxDepth(root.left), maxDepth(root.right))

# BFS
from collections import deque
def maxDepthBFS(root):
    if not root: return 0
    queue = deque([root]); depth = 0
    while queue:
        depth += 1
        for _ in range(len(queue)):
            node = queue.popleft()
            if node.left: queue.append(node.left)
            if node.right: queue.append(node.right)
    return depth