530.二叉搜索树的最小绝对值差

思路：

1. 使用链表收集中序遍历出来的二叉树的节点的值
2. 创建新的数组收集每相邻两个值的差
3. 返回数组的最小值即可

代码实现

/**
 * 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 {
    public int getMinimumDifference(TreeNode root) {
        LinkedList<Integer> list = new LinkedList<>();
        list = inorder(root, list);
        int[] arr = new int[list.size() - 1];
        for (int i = 0; i < arr.length; i++) {
        	arr[i] = list.get(i+1) - list.get(i);
        }
        int min = arr[0];
        for (int i = 0; i < arr.length; i++) {
        	if (arr[i] < min) min = arr[i];
        }
        return min;
    }
	
	public LinkedList<Integer> inorder(TreeNode root, LinkedList<Integer> list) {
        if (root == null) return null;
        
		inorder(root.left, list);
		list.add(root.val);
		inorder(root.right, list);
		
		return list;
	}
}