Binary Search Tree: Insert, Search, Delete

Implement a BST class (no balancing) storing unique integer keys:

• insert(key) (ignore duplicates), contains(key)
• delete(key): handle a leaf, a node with one child, and a node with two children (replace it with its in-order successor); no error if missing
• inorder(): keys in sorted order
• height(): number of nodes on the longest root-to-leaf path (0 for empty)