LeetCode-in-Java

530. Minimum Absolute Difference in BST

Easy

Given the root of a Binary Search Tree (BST), return the minimum absolute 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:

Note: This question is the same as 783: https://leetcode.com/problems/minimum-distance-between-bst-nodes/

Solution

import com_github_leetcode.TreeNode;

/*
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
public class Solution {
    private int ans = Integer.MAX_VALUE;
    private int prev = Integer.MAX_VALUE;

    public int getMinimumDifference(TreeNode root) {
        if (root == null) {
            return ans;
        }
        getMinimumDifference(root.left);
        ans = Math.min(ans, Math.abs(root.val - prev));
        prev = root.val;
        getMinimumDifference(root.right);
        return ans;
    }
}