Leetcode：Convert Sorted List to Binary Search Tree

Convert Sorted List to Binary Search Tree

Given
a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST.

解析：将链表转化为二分查找树，使用递归依次找到中点生成树节点即可

代码：

/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public TreeNode sortedListToBST(ListNode head) {

return build(head);
}

private TreeNode build(ListNode n)
{
if(n==null)return null;
if(n.next==null)
{
TreeNode root = new TreeNode(n.val);
return root;
}
ListNode fast = n;
ListNode slow = n;
ListNode dummy = new ListNode(0);
dummy.next = n;
ListNode pre = dummy;

while(fast!=null&&fast.next!=null)
{pre = pre.next;slow = slow.next;fast = fast.next.next;}
TreeNode root = new TreeNode(slow.val);
pre.next = null;
root.left = build(n);
root.right = build(slow.next);
return root;
}
}