bstToDoublyList
bstToDoublyList#
1 描述#
将一个二叉查找树按照中序遍历转换成双向链表。
2 样例#
给定一个二叉查找树:
4 / \ 2 5 / \ 1 3
返回 1<->2<->3<->4<->5
。
3 解决方案#
做一个中序递归,用head保存首节点,用tail不断更新之后的每个节点。
/** * Definition of TreeNode: * public class TreeNode { * public int val; * public TreeNode left, right; * public TreeNode(int val) { * this.val = val; * this.left = this.right = null; * } * } * Definition for Doubly-ListNode. * public class DoublyListNode { * int val; * DoublyListNode next, prev; * DoublyListNode(int val) { * this.val = val; * this.next = this.prev = null; * } * } */ public class Solution { private DoublyListNode head = null; private DoublyListNode tail = null; /** * @param root: The root of tree * @return: the head of doubly list node */ public DoublyListNode bstToDoublyList(TreeNode root) { // Write your code here if (null == root) { return null; } bstToDoublyList(root.left); DoublyListNode node = new DoublyListNode(root.val); if (null == head) { head = node; tail = node; } else { tail.next = node; node.prev = tail; tail = node; } bstToDoublyList(root.right); return head; } }
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