530. 二叉搜索树的最小绝对差

好家伙

思想：二叉搜索树的中序遍历结果是升序的，将遍历结果存到list中，再相邻的值相减，查找最小值

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
        List<Integer> list = new ArrayList();
        public int getMinimumDifference(TreeNode root) {
            inorder(root);
            int min = list.get(list.size() - 1)-list.get(list.size() - 2);
            for (int i = list.size()-1; i > 0; i--){
                if (list.get(i)-list.get(i-1) < min) min = list.get(i)-list.get(i-1);
            }
            return min;

        }
        public void inorder(TreeNode root){
            if (root == null) return;
            inorder(root.left);
            list.add(root.val);
            inorder(root.right);
        }
    }

如果你有更加低的时间/空间复杂度的算法，欢迎在评论区讨论。

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