235. Lowest Common Ancestor of a Binary Search Tree.cpp

/**
 * 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) {
        if ((root -> val > p -> val) && (root -> val > q -> val)) {
            return lowestCommonAncestor(root -> left, p, q);
        }
        if ((root -> val < p -> val) && (root -> val < q -> val)) {
            return lowestCommonAncestor(root -> right, p, q);
        }
        return root;
    }
};