題目說明

將一個 linkedlist 反轉

解題思路

這題算是基本題，沒有太多訣竅，主要就是要先用一個變數記住 previous node

程式碼

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
        prev = None
        current = head
        
        while current:
            next_node = current.next
            current.next = prev
            prev = current
            current = next_node
            
            
        return prev