LeetCode 235: Lowest Common Ancestor of a Binary Search Tree Solution

Master LeetCode problem 235 (Lowest Common Ancestor of a Binary Search Tree), 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.

235. Lowest Common Ancestor of a Binary Search Tree

Medium

Tree Depth-First Search Binary Search Tree Binary Tree

Problem Explanation

Explanation

To find the lowest common ancestor (LCA) of two given nodes in a binary search tree (BST), we can utilize the properties of a BST. The key idea is to traverse the tree starting from the root and search for a node p and a node q such that their values lie within the range of the current node's value. This way, we can determine the LCA by following the path where the values of p and q diverge.

Start from the root node.
If both p and q are greater than the current node's value, move to the right subtree.
If both p and q are smaller than the current node's value, move to the left subtree.
If the current node's value lies between p and q, then the current node is the LCA.
Return the LCA node.

The time complexity for this approach is O(h), where h is the height of the tree. In the worst case, the height of a BST can be O(n), where n is the number of nodes in the tree, making the time complexity O(n). The space complexity is O(1) as we are using constant extra space for the algorithm.

Solution Code

public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
    while (root != null) {
        if (p.val < root.val && q.val < root.val) {
            root = root.left;
        } else if (p.val > root.val && q.val > root.val) {
            root = root.right;
        } else {
            return root;
        }
    }
    return null;
}

Try It Yourself

Loading code editor...

Frequently Asked Questions

How to solve LeetCode 235 (Lowest Common Ancestor of a Binary Search Tree)?

This page provides optimized solutions for LeetCode problem 235 (Lowest Common Ancestor of a Binary Search Tree) in Java, C++, and Python, along with a detailed explanation and an interactive code editor to test your code.

What is the time complexity of LeetCode 235 (Lowest Common Ancestor of a Binary Search Tree)?

The time complexity for LeetCode 235 (Lowest Common Ancestor of a Binary Search Tree) varies by solution. Check the detailed explanation section for specific complexities in Java, C++, and Python implementations.

Can I run code for LeetCode 235 on DevExCode?

Yes, DevExCode provides an interactive code editor where you can write, test, and run your code for LeetCode 235 in Java, C++, or Python.

Back to LeetCode Solutions