Wins the offer - 59 k-th largest node binary search tree

Title Description

Given a binary search tree, please find the first k smaller nodes therein. For example, (5,3,7,2,4,6,8), the numerical values ​​according to the third junction point is 4 summary.

 

answer:

　　Study is preorder

　　But pay attention to prune

　　

. 1  class Solution {
 2  public :
 . 3      the TreeNode KthNode * (* PROOT the TreeNode, int K)
 . 4      {
 . 5          IF (PROOT == nullptr a) return nullptr a;
 . 6          inOrder (PROOT, K);
 . 7          return RES;
 . 8      }
 . 9      void inOrder ( * PROOT the TreeNode, const  int K)
 10      {
 . 11          IF (n-> == K || PROOT nullptr a) return ; // prune and boundary processing 
12 is          inOrder (pRoot-> left, K);
13         ++n;
14         if (n == k && res == nullptr)
15         {
16             res = pRoot;
17             return;
18         }
19         inOrder(pRoot->right, k);
20     }
21 private:
22     int n = 0;
23     TreeNode *res = nullptr;
24 };