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Given a binary search tree, write a function kthSmallest to find the kth smallest element in it.
Note:
You may assume k is always valid, 1 ≤ k ≤ BST‘s total elements.
Follow up:
What if the BST is modified (insert/delete operations) often and you need to find the kth smallest frequently? How would you optimize the kthSmallest routine?
Hint:
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public int res = 0;
public int counter = 0;
public int kthSmallest(TreeNode root, int k) {
inOrderK(root, k);
return res;
}
public void inOrderK(TreeNode root, int k){
if(root.left!=null) inOrderK(root.left, k);
counter++;
if(counter == k) {
res = root.val;
return;
}
if(root.right!=null) inOrderK(root.right, k);
}
}版权声明：本文为博主原创文章，未经博主允许不得转载。
LeetCode Kth Smallest Element in a BST
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原文地址：http://blog.csdn.net/yangliuy/article/details/46954867
