LeetCode 203————チェーンテーブル要素python(再帰非再帰)を除去する

非再帰

#Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def removeElements(self, head, val):
        """
        :type head: ListNode
        :type val: int
        :rtype: ListNode
        """
        if not head:
            return None
        first = ListNode(-1)   # first     
        first.next = head
        p, q = first, head    # p,q          p             q                 val
        while q:
            if q.val ==val:
                p.next = q.next
                q = q.next
            else:
                q = q.next
                p = p.next
        return first.next

再帰

#Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def removeElements(self, head, val):
        """
        :type head: ListNode
        :type val: int
        :rtype: ListNode
        """
        if not head:
            return None
        
        head.next = self.removeElements(head.next,val)  #                 
        return head.next if head.val == val else head