Increasing Order Search Tree

把一个BST树改写成链表. 这个我用的是dummy node的思路, 建个dummy node然后一点点依照题目构建答案.

class Solution {
    TreeNode p = new TreeNode(-1);
    TreeNode dummy = p;
    public TreeNode increasingBST(TreeNode root) {
        inorder(root);
        return dummy.right;
    }
    
    private void inorder(TreeNode root) {
        if(root == null)
            return;
        inorder(root.left);
        p.right = new TreeNode(root.val);
        p = p.right;
        inorder(root.right);
    }
}