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530. Minimum Absolute Difference in BST ​

题目 ​

Given the root of a Binary Search Tree (BST), return the minimum absolute difference between the values of any two different nodes in the tree.

 

Example 1:

Input: root = [4,2,6,1,3]
Output: 1

Example 2:

Input: root = [1,0,48,null,null,12,49]
Output: 1

 

Constraints:

  • The number of nodes in the tree is in the range [2, 104].
  • 0 <= Node.val <= 105

 

Note: This question is the same as 783: https://leetcode.com/problems/minimum-distance-between-bst-nodes/

Related Topics
  • 树
  • 深度优先搜索
  • 广度优先搜索
  • 二叉搜索树
  • 二叉树

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    • 思路 ​

    BST 中序列遍历即可得到一个从 asc 的队列，比较 asc 队列的前后差值即可找到最小值

    解法 ​

    py
    # leetcode submit region begin(Prohibit modification and deletion)
# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def getMinimumDifference(self, root: Optional[TreeNode]) -> int:
        self.res = float('inf')
        self.pre = None
        def dfs(node: Optional[TreeNode]):
            if not node:
                return

            dfs(node.left)
            if self.pre is not None:
                self.res = min(self.res, abs(node.val - self.pre))
            self.pre = node.val
            dfs(node.right)


        dfs(root)
        return self.res

        
# leetcode submit region end(Prohibit modification and deletion)

    复杂度分析 ​

    • 时间复杂度 O(N)
    • 空间复杂度 O(N)