235.lowest-common-ancestor-of-a-binary-search-tree.cpp

/*
 * @lc app=leetcode id=235 lang=cpp
 *
 * [235] Lowest Common Ancestor of a Binary Search Tree
 */

// @lc code=start
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */

class Solution
{
public:
    TreeNode *lowestCommonAncestor(TreeNode *root, TreeNode *p, TreeNode *q)
    {

        while (root != NULL)
        {
            // basecase there is a split
            if (p->val <= root->val && q->val >= root->val || p->val >= root->val && q->val <= root->val)
            {
                return root;
            }
            else 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;
            }
        }
        return root;
    }
};
// @lc code=end