[235] Lowest Common Ancestor of a Binary Search Tree

 1 class Solution {
 2 public:
 3     TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
 4         
 5         assert( p != NULL && q != NULL );
 6         
 7         if( root == NULL )
 8             return NULL;
 9         
10         if( p->val < root->val && q->val < root->val )
11             return lowestCommanAncestor( root->left , p , q );
12         if( p->val > root->val && q->val > root->val )
13             return lowestCommanAncestor( root->right , p , q );
14             
15         return root;
16     }    
17 };