二叉树最近公共祖先（LeetCode）

 1 /**
 2  * Definition for a binary tree node.
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
13         if(root==NULL || root==p || root==q)//base case
14             return root;
15         TreeNode *left = lowestCommonAncestor(root->left, p, q);
16         TreeNode *right = lowestCommonAncestor(root->right, p, q);
17         if(left!=NULL && right!=NULL){
18             return root;
19         }
20         return left!=NULL?left:right;
21     }
22 };