【编程题】二叉树最近公共父亲节点

 //Definition for a binary tree node.
 struct TreeNode {
    int val;
     TreeNode *left;
     TreeNode *right;
     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 };

TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {

if (root == NULL)
return NULL;
if (root == p || root == q)
return root;
TreeNode* left = lowestCommonAncestor(root->left, p, q);
TreeNode* right = lowestCommonAncestor(root->right, p, q);

if (left != NULL &&right != NULL)
return root;
else
return left != NULL? left:right;

}