01. 链表双指针知识

[utterances-bot]

01.链表双指针知识 | 算法通关手册

链表双指针知识 # 1. 双指针简介 # 在数组双指针中我们已经学习过了双指针的概念。这里再来复习一下。
双指针（Two Pointers）：指的是在遍历元素的过程中，不是使用单个指针进行访问，而是使用两个指针进行访问，从而达到相应的目的。如果两个指针方向相反，则称为「对撞时针」。如

https://algo.itcharge.cn/02.Linked-List/03.Linked-List-Two-Pointers/01.Linked-List-Two-Pointers/

[nicehuster]

class Solution:
    def hasCycle(self, head: ListNode) -> bool:
        if not head or not head.next: return False
        slow = fast = head
        while fast.next and fast.next.next:
            fast = fast.next.next
            slow = slow.next
            if slow==fast: return True

        return False

[Shi-Tank]

class Solution:
    def removeNthFromEnd(self, head: ListNode, n: int) -> ListNode:
        newHead = ListNode(0, head)
        fast = head   # 这里应该是 fast = newHead  快慢指针都从newHead出发吧 
        slow = newHead
        while n:
            fast = fast.next
            n -= 1
        while fast:
            fast = fast.next
            slow = slow.next
        slow.next = slow.next.next
        return newHead.next