Introduction

In this blog post, we will explore how to solve the LeetCode problem "3217" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

You are given an array of integers nums and the head of a linked list. Return the head of the modified linked list after removing all nodes from the linked list that have a value that exists in nums. Example 1: Input: nums = [1,2,3], head = [1,2,3,4,5] Output: [4,5] Explanation: Remove the nodes with values 1, 2, and 3. Example 2: Input: nums = [1], head = [1,2,1,2,1,2] Output: [2,2,2] Explanation: Remove the nodes with value 1. Example 3: Input: nums = [5], head = [1,2,3,4] Output: [1,2,3,4] Explanation: No node has value 5. Constraints: 1 <= nums.length <= 105 1 <= nums[i] <= 105 All elements in nums are unique. The number of nodes in the given list is in the range [1, 105]. 1 <= Node.val <= 105 The input is generated such that there is at least one node in the linked list that has a value not present in nums.

Explanation

Here's the solution:

• Convert nums to a Set: Create a set from the nums array for O(1) average time complexity lookups. This is much faster than searching the array repeatedly.
• Iterate and Remove: Iterate through the linked list, using a "dummy head" to simplify removing the actual head of the list if needed. If a node's value is in the set, remove it by adjusting the next pointer of the previous node.

• Return Modified Head: Return the next pointer of the dummy head, which will be the new head of the modified list.

• Time Complexity: O(N + M), where N is the length of the linked list and M is the length of the nums array. Space Complexity: O(M), for storing the nums in a set.

Code

    class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

def remove_nodes(nums, head):
    """
    Removes nodes from a linked list whose values are present in a given array.

    Args:
        nums: A list of integers.
        head: The head of the linked list.

    Returns:
        The head of the modified linked list.
    """

    nums_set = set(nums)
    dummy_head = ListNode(0)  # Dummy node to handle removal of the head
    dummy_head.next = head
    current = dummy_head

    while current.next:
        if current.next.val in nums_set:
            current.next = current.next.next  # Remove the node
        else:
            current = current.next  # Move to the next node

    return dummy_head.next  # Return the new head of the list