Yosgi Siqi Liu

Counting nodes in a complete binary tree using left/right subtree depths instead of a full DFS.

Computing the maximum width of a binary tree with BFS, tracking each node's position index within its level.

Finding all nodes at distance K by first adding parent links with DFS, then searching outward from the target.

Validating a binary search tree by exploiting the increasing order of its in-order traversal.

Restoring a BST with two swapped nodes by locating them during an in-order traversal.

Deleting a node from a binary search tree by locating it via the BST property, then handling the three deletion cases.

Trimming a BST to a value range by recursing into the correct branch using the BST bounds.

Constructing a binary search tree from its pre-order sequence by recursively inserting each value.

Connecting each node to its right neighbor per level, reusing the previous layer's links to reach constant space.

Generating all possible full binary trees with recursion that combines left and right subtree counts (DP).