783. 二叉搜寻树节点最小间隔给你一个二叉搜寻树的根节点 root ,返回 树中任意两不同节点值之间的最小差值 。留神:本题与 530:https://leetcode-cn.com/problems/minimum-absolute-difference-in-bst/ 雷同示例 1:输出:root = [4,2,6,1,3]输入:1示例 2:输出:root = [1,0,48,null,null,12,49]输入:1class Solution {    //DFS    TreeNode pre;    int min = Integer.MAX_VALUE;    public int minDiffInBST(TreeNode root) {        dfs(root);        return min;    }    public void dfs(TreeNode root){        if(root == null) return;        dfs(root.left);        if(pre != null) min = Math.min(min,root.val - pre.val);         pre = root;        dfs(root.right);    }}