230. Kth Smallest Element in a BST
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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.
Example 1:
Input: root = [3,1,4,null,2], k = 1
3
/ \
1 4
\
2
Output: 1
Example 2:
Input: root = [5,3,6,2,4,null,null,1], k = 3
5
/ \
3 6
/ \
2 4
/
1
Output: 3
class Solution:
def kthSmallest(self, root):
self.k = k
self.ans = root.val
traverse(root)
return self.ans
def traverse(self, root):
if not root:
return
traverse(root.left)
self.k -= 1
if not self.k:
self.ans = root.val
else:
traverse(root.right)