Delete Node in a Linked List Python Solution

Tested Python solution for LeetCode 237 with 15 pytest cases. Generate a practice environment with lcpy.

LeetCode 237, Medium. Topics: Linked List. View on LeetCode.

Generate this problem as a practice environment: tested reference solution, 15 parametrized pytest cases, and a playground notebook:

lcpy gen -n 237   # by problem number
lcpy gen -s delete_node_in_a_linked_list   # by problem name

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Problem

There is a singly-linked list head and we want to delete a node node in it.

You are given the node to be deleted node. You will not be given access to the first node of head.

All the values of the linked list are unique, and it is guaranteed that the given node node is not the last node in the linked list.

Delete the given node. Note that by deleting the node, we do not mean removing it from memory. We mean:

• The value of the given node should not exist in the linked list.
• The number of nodes in the linked list should decrease by one.
• All the values before node should be in the same order.
• All the values after node should be in the same order.

Custom testing:

• For the input, you should provide the entire linked list head and the node to be given node. node should not be the last node of the list and should be an actual node in the list.
• We will build the linked list and pass the node to your function.
• The output will be the entire list after calling your function.

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Examples

Input: head = [4,5,1,9], node = 5
Output: [4,1,9]
Explanation: You are given the second node with value 5, the linked list should become 4 -> 1 -> 9 after calling your function.

Input: head = [4,5,1,9], node = 1
Output: [4,5,9]
Explanation: You are given the third node with value 1, the linked list should become 4 -> 5 -> 9 after calling your function.

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Constraints

• The number of the nodes in the given list is in the range [2, 1000].
• -1000 <= Node.val <= 1000
• The value of each node in the list is unique.
• The node to be deleted is in the list and is not a tail node.

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Solution

Reference implementation from solution.py on GitHub, full suite in test_solution.py:

from leetcode_py import ListNode


class Solution:
    # Time: O(1)
    # Space: O(1)
    def delete_node(self, node: ListNode[int]) -> None:
        # Given node is never the tail, so copy the successor into it and skip it
        nxt = node.next
        if nxt is None:
            return
        node.val = nxt.val
        node.next = nxt.next

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Complexity

Time	Space
O(1)	O(1)

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