LeetCode Lowest Common Ancestor of a Binary Search Tree （LCA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) {  //这是一棵排序树啊！
13         if( (root->val - p->val ) * (root->val - q->val) <=0  )    //一大一小必会产生负的，或者root为其中1个，那么就是0
14             return root;
15         if( max(p->val, q->val) < root->val )              //都在左边
16             return lowestCommonAncestor(root->left, p, q);
17         else            //都在右边
18             return lowestCommonAncestor(root->right, p, q);
19     }
20 };