【剑指offer】二叉搜索树的第k个结点

 1 /*
 2 struct TreeNode {
 3     int val;
 4     struct TreeNode *left;
 5     struct TreeNode *right;
 6     TreeNode(int x) :
 7             val(x), left(NULL), right(NULL) {
 8     }
 9 };
10 */
11 class Solution {
12 public:
13     int cnt = 0;
14     TreeNode* KthNode(TreeNode* pRoot, int k){
15         if(pRoot == NULL || k <= 0)    return NULL;
16         //中序遍历
17         TreeNode* node = KthNode(pRoot->left,k);    //左子树找
18         if(node)    return node; //左子树中找到
19         if(++cnt == k)    return pRoot;        //根结点
20         node = KthNode(pRoot->right,k);        //右子树找
21         if(node)    return node;//右子树找到
22     }
23 
24     
25 };