Leetcode 1028. Recover a Tree From Preorder Traversal

Reconstruct a binary tree from a preorder string where each node is represented by its value prefixed with D dashes indicating its depth (root depth 0) and any single child is guaranteed to be the left child. The challenge is to parse depth/value pairs and attach nodes at the correct depths (e.g., via a depth-indexed stack or recursive construction) to rebuild and return the tree.