Binary Trees — Recursion Native

Answer for a node from left + right children.

When to use this

Depth
Invert
Same / symmetric

C++ template

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

Dry run

Root with deeper right child → depth = 1 + max(L,R).

Pitfalls

Null base case
Swap order
BFS/DFS confusion

Say this in the interview

Null base, combine children.

Problems in this topic (3)

Each opens teach-first (animated when available), then the code panel.