4 articles
LC 337 House Robber III extends the classic House Robber DP to a binary tree where adjacent nodes cannot both be robbed. The optimal O(n) solution uses post-order DFS returning a (rob, skip) pair — a fundamental tree DP pattern tested at Amazon and Microsoft.
LC 968 Binary Tree Cameras asks for the minimum number of cameras to monitor all nodes. The O(n) greedy solution assigns three states per node in a bottom-up DFS — delay camera placement as high as possible, a pattern tested at Amazon and Google.
LC 124 Binary Tree Maximum Path Sum finds the highest-value path in a binary tree where the path can start and end at any node. The O(n) solution uses a post-order DFS that tracks the global max while returning only one branch to the parent — a critical FAANG interview problem at Amazon, Google, and Facebook.
LC 1373 Maximum Sum BST in Binary Tree finds the highest sum among all BST subtrees of a binary tree. The O(n) solution uses post-order DFS returning a 4-tuple of (is_bst, min, max, sum) metadata — a hard FAANG problem tested at Amazon and Google.