Problem: Minimum Distance Between BST Nodes

Question

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.

Solution

Inorder traversal.

Code

Here is a sample solution.

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    int min = Integer.MAX_VALUE;
    Integer prev = null;
    public int minDiffInBST(TreeNode root) {
        inorder(root);
        return min;
    }

    private void inorder(TreeNode root) {
        if(root == null) return;
        inorder(root.left);
        if(prev != null) {
            min = Math.min(min, root.val - prev);
        }
        prev = root.val;
        inorder(root.right);
    }
}

Performance

O(n)

Problem: Minimum Distance Between BST Nodes

Question

Solution

Code

Performance

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