235. Lowest Common Ancestor of a Binary Search Tree

/**
* 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) return NULL;
if(root==p||root==q) return root;
TreeNode* l=lowestCommonAncestor(root->left,p,q);
TreeNode* r=lowestCommonAncestor(root->right,p,q);
if(!l&&!r) return NULL;
else if(!l&&r) return r;
else if(l&&!r) return l;
else return root;
}
};