原题
https://leetcode-cn.com/problems/middle-of-the-linked-list/
解题思路
用快慢指针,快的一次前进两格,慢的一次前进一格。
代码
/**
* Definition for singly-linked list.
* function ListNode(val) {
* this.val = val;
* this.next = null;
* }
*/
/**
* @param {ListNode} head
* @return {ListNode}
*/
var middleNode = function(head) {
if (!head || !head.next) return head;
let slow = head, fast = head.next;
while (fast) {
slow = slow.next;
if (fast.next) {
fast = fast.next.next;
} else {
fast = null;
}
}
return slow;
};
复杂度
- 时间复杂度 O(N)
- 空间复杂度 O(1)