题解 | #二叉搜索树与双向链表#

pre记录上次的节点，head记录头节点

public class Solution {
    
    TreeNode head = null,pre =null;
    
    public void dfs(TreeNode root){
        if(root == null)return;
        dfs(root.left);
        if(head == null)head = root;
        else pre.right = root;
        root.left = pre;
        pre = root;
        dfs(root.right);
    }
    
    
    public TreeNode Convert(TreeNode pRootOfTree) {
        if(pRootOfTree == null)return null;
        dfs(pRootOfTree);
        return head;
    }
}