LeetCode 450: Delete Node in a BST Solution

Master LeetCode problem 450 (Delete Node in a BST), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

450. Delete Node in a BST

Medium

Tree Binary Search Tree Binary Tree

Problem Explanation

Explanation

To delete a node in a binary search tree (BST), we need to find the node with the given key and perform the deletion. There are three cases to consider:

If the node to be deleted has no children, we simply remove the node.
If the node to be deleted has one child, we replace the node with its child.
If the node to be deleted has two children, we find the inorder successor (smallest node in the right subtree), copy its value to the node to be deleted, and then recursively delete the inorder successor.

Time complexity: O(h), where h is the height of the tree. Space complexity: O(h) for the recursive call stack.

Solution Code

class Solution {
    public TreeNode deleteNode(TreeNode root, int key) {
        if (root == null) return null;
        
        if (key < root.val) {
            root.left = deleteNode(root.left, key);
        } else if (key > root.val) {
            root.right = deleteNode(root.right, key);
        } else {
            if (root.left == null) {
                return root.right;
            } else if (root.right == null) {
                return root.left;
            }
            
            TreeNode minNode = findMin(root.right);
            root.val = minNode.val;
            root.right = deleteNode(root.right, root.val);
        }
        
        return root;
    }
    
    private TreeNode findMin(TreeNode node) {
        while (node.left != null) {
            node = node.left;
        }
        return node;
    }
}

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