235. Lowest Common Ancestor of a Binary Search Tree - BST Property.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 || root == p || root == q) return root;
        int max = p->val > q->val ? p->val : q->val;
        int min = p->val > q->val ? q->val : p->val;
        if(min < root->val && root->val < max) return root;
        else if(root->val >= max) return lowestCommonAncestor(root->left, p, q);
        return lowestCommonAncestor(root->right, p, q);
    }
};