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;

    }

}
*/

// 这道题要用到 中序遍历
public class Solution {
    public TreeNode head = null, pre = null;
    // head 是最左边的那个节点，pre 是从左往右开始的前一个节点
    public TreeNode Convert(TreeNode pRootOfTree) {
        if(pRootOfTree == null){
            return null;
        }
        inOrderT(pRootOfTree);
        return head;

    }
    public void inOrderT(TreeNode root){
        if(root == null){
            return;
        }
        inOrderT(root.left);
        if(pre == null){
            head = root;
        }else{
            pre.right = root;
        }
        root.left=pre;
        pre = root;
        inOrderT(root.right);

    }
    
    
}