LeetCode 530. Minimum Absolute Difference in BST

Description

https://leetcode.com/problems/minimum-absolute-difference-in-bst/

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/

Explanation

Traverse to get node values and then find the minimum distance between node values.

Python Solution

# 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: TreeNode) -> int:
        self.results = []
        
        self.traverse(root)
        
        
        self.results = sorted(self.results)
        
        prev = None
        
        min_distance = sys.maxsize
        for val in self.results:
            if prev != None:
                min_distance = min(min_distance, val - prev)
            prev = val

        return min_distance
    
    
    def traverse(self, root):
        if not root:
            return
        
        self.results.append(root.val)        
        self.traverse(root.left)
        self.traverse(root.right)
  • Time Complexity: O(N).
  • Space Complexity: O(N).

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