BST的最小绝对差

题目：给一颗BST，找两个节点最小绝对值的差

思路：遍历一下，再扫一遍就行。。。。。

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    
    ArrayList<Integer> nodes = new ArrayList<Integer>();
        
    public int getMinimumDifference(TreeNode root) {
        getNodes(root);
        int res = Integer.MAX_VALUE;
        for(int i = 1;i < nodes.size();i++){
            Integer resid = nodes.get(i) - nodes.get(i-1);
            if(resid < res)
            res = resid;
        }
        return res;
    }
    public void getNodes(TreeNode root){
        if(root != null){
            getNodes(root.left);
            nodes.add(root.val);
            getNodes(root.right);
        }
    }
}