定义前置指针,记录上一个值,遍历链表,获取要删除的节点

# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
#
# 代码中的类名、方法名、参数名已经指定,请勿修改,直接返回方法规定的值即可
#
# 
# @param head ListNode类 
# @param val int整型 
# @return ListNode类
#
class Solution:
    def deleteNode(self , head: ListNode, val: int) -> ListNode:
        # write code here
        if head.val == val: return head.next
        head_new = head
        pre_node = ListNode(-1)
        pre_node.next = head_new
        while head_new and head_new.val != val:
            pre_node = pre_node.next
            head_new = head_new.next
        pre_node.next = head_new.next
        return head