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