236-二叉树的最近公共祖先

 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)
14         {
15             return NULL;
16         }
17         if(root==p||root==q)
18         {
19             return root;
20         }
21         TreeNode* left1=lowestCommonAncestor(root->left,p,q);
22         TreeNode* right1=lowestCommonAncestor(root->right,p,q);
23         if(left1==NULL)
24         {
25             return right1;
26         }
27         if(right1==NULL)
28         {
29             return left1;
30         }
31         if(left1&&right1)
32         {
33             return root;
34         }
35         return NULL;
36 
37         
38     }
39 };