530. Minimum Absolute Difference in BST

难度: Easy

题目描述

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:

• The number of nodes in the tree is in the range [2, 104].
• 0 <= Node.val <= 105

 

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

解题思路

代码实现

解决方案

java

/**
 * 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;
 * }
 * }
 */
class Solution {
    int min = Integer.MAX_VALUE;
    TreeNode pre;

    public int getMinimumDifference(TreeNode root) {
        dfs(root);
        return min;
    }

    public void dfs(TreeNode root) {
        if (root == null) {
            return;
        }

        if (pre == null) {
            pre = root;
        }
        TreeNode left = root.left;
        TreeNode right = root.right;
        dfs(left);
        if (pre != null && pre != root) {
            min = Math.min(min, Math.abs(pre.val - root.val));
            pre = root;
        }

        dfs(right);

    }
}