How should I practice Delete Node in a BST?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Tokopedia phone screen problems in FastPrep.

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Delete Node in a BST

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Problem statement

You are given the root of a binary search tree and an integer key. Delete the node whose value equals key, if it exists, and return the updated root.

The returned tree must remain a binary search tree. When the deleted node has two children, replace its value with the smallest value in its right subtree, then delete that successor node. This deterministic canonical strategy fixes one serialized output for the runner.

Function

deleteNode(root: TreeNode, key: int) → TreeNode

Examples

Example 1

root = [5,3,6,2,4,null,7]key = 3return = [5,4,6,2,null,null,7]

Node 3 has two children. Its inorder successor is 4, which takes its place.

Example 2

root = [5,3,6,2,4,null,7]key = 0return = [5,3,6,2,4,null,7]

The key is absent, so the tree is unchanged.

Example 3

root = []key = 0return = []

An empty tree remains empty.

Constraints

The tree contains between 0 and 10000 nodes.
-100000 <= Node.val <= 100000.
Every node value is unique and the input is a valid binary search tree.
-100000 <= key <= 100000.