# Minimum Distance Between BST Nodes

#1

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.

#2

Since it is a BST, an inorder traversal gives us a sorted ascending order of values. So we keep track of the diff between the last value and the current value in the min and return it.

``````/**
* Definition for a binary tree node.
* type TreeNode struct {
*     Val int
*     Left *TreeNode
*     Right *TreeNode
* }
*/
func minDiffInBST(root *TreeNode) int {

prev := math.MinInt32
min := math.MaxInt32
helper(root, &prev, &min)
return min
}

func helper(root *TreeNode, prev, min *int){
if(root==nil){return}
helper(root.Left, prev, min)
if(*min > root.Val - *prev){
*min = root.Val - *prev
}
*prev = root.Val

helper(root.Right, prev, min)
}

``````