783. Minimum Distance Between BST Nodes

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

Example :

Input: root = [4,2,6,1,3,null,null]
Output: 1
Explanation:
Note that root is a TreeNode object, not an array.

The given tree [4,2,6,1,3,null,null] is represented by the following diagram:

          4
        /   \
      2      6
     / \
    1   3

while the minimum difference in this tree is 1, it occurs between node 1 and node 2, also between node 3 and node 2.

Note:

1. The size of the BST will be between 2 and 100.
2. The BST is always valid, each node's value is an integer, and each node's value is different.
3. This question is the same as 530: <https://leetcode.comhttps://leetcode.com/problems/minimum-absolute-difference-in-bst/>

# @lc code=start
using LeetCode

function min_diff_in_bst(root::TreeNode)
    prev, ans = typemin(Int) >> 1, typemax(Int)
    function dfs(root::TreeNode)
        (root.left !== nothing) && (dfs(root.left))
        ans = min(root.val - prev, ans)
        prev = root.val
        (root.right !== nothing) && (dfs(root.right))
    end
    dfs(root)
    ans
end
# @lc code=end

min_diff_in_bst (generic function with 1 method)

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