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### by Sumit Chourasia | Oct 09, 2020 | Category :coding | Tags : algorithmbinary-treedata-structureeasyleetcodetree #### Minimum Distance Between BST Nodes - Tree - Easy - LeetCode

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:

The size of the BST will be between 2 and 100.
The BST is always valid, each node's value is an integer, and each node's value is different.

``````/**
* Definition for a binary tree node.
* public class TreeNode {
*     public int val;
*     public TreeNode left;
*     public TreeNode right;
*     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
*         this.val = val;
*         this.left = left;
*         this.right = right;
*     }
* }
*/
public class Solution {
int min=int.MaxValue;
int? prev = null;
public int MinDiffInBST(TreeNode root) {
Helper(root);
return min;
}

private void Helper(TreeNode root){
if(root==null){
return;
}

Helper(root.left);
if(prev!=null){
min = Math.Min(min,root.val-(int)prev);
}
prev = root.val;
Helper(root.right);
}
}``````

Time Complexity: O(n)

Space Complexity: O(1)