[LeetCode] 203. Remove Linked List Elements_Easy tag: Linked LIst

Remove all elements from a linked list of integers that have value val.

Example:

Input:  1->2->6->3->4->5->6, val = 6
Output: 1->2->3->4->5

基本思路就是直接建一个新的head, 然后每次将非val值的node copy进入新head的tail上面.

比较腻害的做法是用DFS的recursive方法.

Code

1) basic

class Solution:
    def remLinkedList(self, head, val):
        ans = dummy = ListNode(1)
        while head:
            if head.val != val:
                dummy.next = ListNode(head.val)
                dummy = dummy.next
            head = head.next
        return ans.next

2) recursive

class Solution:
    def remLinkedList(self, head, val):
        if not head :return
        head.next = self.remLinkedList(head.next, val)
        return head.next if head.val == val else head