203. Remove Linked List Elements

📋 Đề Bài

Given the head of a linked list and an integer val, remove all the nodes of the linked list that has Node.val == val, and return the new head.

Example 1:

Input: head = [1,2,6,3,4,5,6], val = 6
Output: [1,2,3,4,5]

Example 2:

Input: head = [], val = 1
Output: []

Example 3:

Input: head = [7,7,7,7], val = 7
Output: []

Constraints:

The number of nodes in the list is in the range [0, 10⁴].
1 <= Node.val <= 50
0 <= val <= 50

🧠 Thuật Toán & Kỹ Thuật

Linked List (Danh sách liên kết)

⏱️ Thời gian O(n)

💾 Không gian O(n)

💻 Lời Giải

Python 0203-remove-linked-list-elements.py

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def removeElements(self, head: Optional[ListNode], val: int) -> Optional[ListNode]:
        head1 = ListNode(0)
        list1 = head1
        currNode = head
        
        while currNode:
            if currNode.val != val:
                list1.next = ListNode(currNode.val)
                list1 = list1.next
            currNode = currNode.next
            
        return head1.next