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:
solution:
Inorder traverse, get kth element from that result. complexity is O(n)
public class Solution { List<Integer> path = new ArrayList<>(); public int kthSmallest(TreeNode root, int k) { inorder(root); return path.get(k-1); } public void inorder(TreeNode root) { if(root != null){ inorder(root.left); path.add(root.val); inorder(root.right); } } }
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[LeetCode 230] Kth Smallest Element in a BST
原文地址:http://blog.csdn.net/sbitswc/article/details/48544731