LeetCode876:Middle of the Linked List
阿新 • • 發佈:2018-12-18
Given a non-empty, singly linked list with head node head
, return a middle node of linked list.
If there are two middle nodes, return the second middle node.
Example 1:
Input: [1,2,3,4,5] Output: Node 3 from this list (Serialization: [3,4,5]) The returned node has value 3. (The judge's serialization of this node is [3,4,5]). Note that we returned a ListNode object ans, such that: ans.val = 3, ans.next.val = 4, ans.next.next.val = 5, and ans.next.next.next = NULL.
Example 2:
Input: [1,2,3,4,5,6] Output: Node 4 from this list (Serialization: [4,5,6]) Since the list has two middle nodes with values 3 and 4, we return the second one.
我的方法好笨,就是先遍歷一遍得到長度,然後再求中值,再遍歷==
正確的做法:設定兩個快慢指標,慢的每次走一步,快的每次走兩步。當快的指標到達尾部時,慢的指標就是要求的值了,返回即可。但是要判斷快指標是在連結串列尾部還是None。