[LeetCode] Reverse Linked List 파이썬

iterative way

# 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: ListNode) -> ListNode:
        prev = None
        curr = head
        
        while curr:
            nxt = curr.next
            curr.next = prev
            prev = curr
            curr = nxt
        return prev

 

recursive way

class Solution:
    # @param {ListNode} head
    # @return {ListNode}
    def reverseList(self, head):
        return self.reverse_recu(head, None)
    
    def reverse_recu(self, cur, prev):
        if not cur:
            return prev

        nxt = cur.next
        cur.next = prev # point backward
        prev = cur
        cur = nxt
        return self.reverse_recu(cur, prev)
    
    
        

 

www.youtube.com/watch?v=O0By4Zq0OFc