题解 | #二叉搜索树与双向链表#

import java.util.*;
/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {
    private TreeNode head = null;

    private TreeNode pre = null;
    
    public TreeNode Convert(TreeNode pRootOfTree) {
        if (pRootOfTree == null) {
            return pRootOfTree;
        }
        Convert(pRootOfTree.left);
        if (pre == null) {
            head = pRootOfTree;
            pre = pRootOfTree;
        } else {
            pre.right = pRootOfTree;
            pRootOfTree.left = pre;
            pre = pRootOfTree;
        }
        Convert(pRootOfTree.right);
        return head;
    }
}