LeetCode 783. Minimum Distance Between BST Nodes

Description

https://leetcode.com/problems/minimum-distance-between-bst-nodes/

Given the root of a Binary Search Tree (BST), return the minimum 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, 100].
  • 0 <= Node.val <= 105

Note: This question is the same as 530: https://leetcode.com/problems/minimum-absolute-difference-in-bst/

Explanation

In order traverse to get values in ascending order. Then find the minimum distance between 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 minDiffInBST(self, root: TreeNode) -> int:
        self.values = []
        
        self.inorder_traverse(root)
        
        min_distance = sys.maxsize
        
        prev = None
        
        for val in self.values:
            if prev:            
                distance = val - prev
                min_distance = min(min_distance, distance)
            prev = val
            
        
        return min_distance
        
    def inorder_traverse(self, root):
        
        if not root:
            return 
        
        
        self.inorder_traverse(root.left)
        self.values.append(root.val)
        
        self.inorder_traverse(root.right)
        
  • Time Complexity: O(N).
  • Space Complexity: O(N).

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