面试题36. 二叉搜索树与双向链表

超、凢脫俗 2023-02-16 01:49 6阅读 0赞

# 题目： #

[面试题36. 二叉搜索树与双向链表][36.]  
[426. 将二叉搜索树转化为排序的双向链表][426.]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 1]

# 题解： #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 2]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 3]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 4]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 5]

# 代码： #

**Node.java**

// Definition for a Node.
    class Node { 
        public int val;
        public Node left;
        public Node right;
    
        public Node() { 
        }
    
        public Node(int _val) { 
            val = _val;
        }
    
        public Node(int _val, Node _left, Node _right) { 
            val = _val;
            left = _left;
            right = _right;
        }
    };

**面试题36.java**

public class 面试题36 { 
    
        public Node pre;
        public Node head;
    
        public Node treeToDoublyList(Node root) { 
            if(root == null)
            { 
                return null;
            }
            dfs(root);
    
            pre.right = head;
            head.left = pre; // 进行头节点和尾节点的相互指向，这两句的顺序也是可以颠倒的
    
            return head;
        }
    
        public void dfs(Node cur)
        { 
            if(cur == null)
            { 
                return;
            }
            dfs(cur.left);
            // pre用于记录双向链表中位于cur左侧的节点，即上一次迭代中的cur,
            // 当pre==null时，cur左侧没有节点,即此时cur为双向链表中的头节点
            if(pre == null)
            { 
                head = cur;
            }
            // 反之，pre!=null时，cur左侧存在节点pre，需要进行pre.right=cur的操作。
            else
            { 
                pre.right = cur;
            }
            cur.left = pre; // pre是否为null对这句没有影响,且这句放在上面两句if else之前也是可以的。
            pre = cur; // pre指向当前的cur
            dfs(cur.right); // 全部迭代完成后，pre指向双向链表中的尾节点
        }
        
        public static void main(String[] args) { 
            
        }    
    }

# 参考： #

1.  [面试题36. 二叉搜索树与双向链表（中序遍历，清晰图解）][36. 1]

[36.]: https://leetcode-cn.com/problems/er-cha-sou-suo-shu-yu-shuang-xiang-lian-biao-lcof/
[426.]: https://leetcode-cn.com/problems/convert-binary-search-tree-to-sorted-doubly-linked-list/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/2020060713043368.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20200607130528314.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3p5eF9seQ==,size_16,color_FFFFFF,t_70
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[36. 1]: https://leetcode-cn.com/problems/er-cha-sou-suo-shu-yu-shuang-xiang-lian-biao-lcof/solution/mian-shi-ti-36-er-cha-sou-suo-shu-yu-shuang-xian-5/