题解 | #二叉搜索树最小差值#

public class Solution {
    public int minDifference (TreeNode root) {
        List<Integer> list = new ArrayList<>();
        // 首先进行中序遍历，二叉搜索树中序遍历的结果是单调递增的
        inOrder(root, list);
        int len = list.size();
        int[] nums = new int[len - 1];
        // 计算出所有差值
        for (int i = 1; i < len; i++) {
            nums[i - 1] = list.get(i) - list.get(i - 1);
        }
        Arrays.sort(nums);
        return nums[0];
    }
    
    private void inOrder(TreeNode root, List<Integer> list) {
        if (root == null) {
            return;
        }
        inOrder(root.left, list);
        list.add(root.val);
        inOrder(root.right, list);
    }
}