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