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64 lines
1.4 KiB
Python
64 lines
1.4 KiB
Python
"""
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230. Kth Smallest Element in a BST
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Difficulty: Medium
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https://leetcode.com/problems/kth-smallest-element-in-a-bst/
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──────────────────────────────────────────────────
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Given the root of a binary search tree, and an integer k, return the
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k^th smallest value (1-indexed) of all the values of the nodes in the
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tree.
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Example 1:
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Input: root = [3,1,4,null,2], k = 1
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Output: 1
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Example 2:
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Input: root = [5,3,6,2,4,null,null,1], k = 3
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Output: 3
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Constraints:
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• The number of nodes in the tree is n.
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• 1 <= k <= n <= 10^4
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• 0 <= Node.val <= 10^4
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Follow up: If the BST is modified often (i.e., we can do insert and
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delete operations) and you need to find the kth smallest frequently,
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how would you optimize?
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"""
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# Definition for a binary tree node.
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# class TreeNode:
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# def __init__(self, val=0, left=None, right=None):
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# self.val = val
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# self.left = left
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# self.right = right
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class Solution:
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def kthSmallest(self, root: Optional[TreeNode], k: int) -> int:
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n = 0
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stack = []
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cur = root
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while cur or stack:
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while cur:
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stack.append(cur)
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cur = cur.left
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cur = stack.pop()
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n += 1
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if n == k:
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return cur.val
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cur = cur.right
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