Question:
Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.
For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.
Example:
Given the sorted linked list: [-10,-3,0,5,9], One possible answer is: [0,-3,9,-10,null,5], which represents the following height balanced BST: 0 / -3 9 / / -10 5
Tips:
给定一个有序的单链表,将其转换成一个平衡二叉查找树。
思路:
(1)找到链表的中间位置,作为BST的根节点。方法就是设置两个指针,fast、slow,slow每次走一步,fast每次走两步。当fast先遇到null,slow就指向链表中间节点。
(2)左、右子树的根节点也用相同的方法找到,并作为根节点的左右子树。接下来的结点可用递归来解决。
代码:
public TreeNode sortedListToBST(ListNode head){ if(head==null) return null; return toBST(head,null); } private TreeNode toBST(ListNode head,ListNode tail) { if(head==tail) return null; ListNode fast=head; ListNode slow=head; //循环找到链表中间位置作为根节点。 while(fast!=tail && fast.next!=tail){ slow=slow.next; fast=fast.next.next; } TreeNode root=new TreeNode(slow.val); root.left=toBST(head,slow); root.right=toBST(slow.next,tail); return root; }
原文地址:https://www.cnblogs.com/yumiaomiao/p/8487890.html
时间: 2024-10-29 03:57:52