LC237. Delete Node in a Linked List¶

Problem Description¶

LeetCode Problem 237: 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.

Clarification¶

Give node to be deleted but not the head
Not remove it from memory just remove the value from the list

Assumption¶

Solution¶

Approach - Delete value¶

Without knowing the previous node, it is not possible to delete the current node. Since the given node is not a tail node and all node values are unique, we can delete the next node instead and coping its value to the current node.

Note

Remember to delete the node from memory.

Python

class Solution:
    def deleteNode(self, node):
        """
        :type node: ListNode
        :rtype: void Do not return anything, modify node in-place instead.
        """

        if node.next:
            next_node = node.next
            node.val = next_node.val
            node.next = next_node.next

            next_node.next = None
            del next_node

Complexity Analysis¶

Time complexity: \(O(1)\)
Since only 1 node is to be deleted.
Space complexity: \(O(1)\)
Use constant space to track the next node.