Cheat Sheet

Linked List Cheat Sheet

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What is Linked List?

Navigate node-based data structures with pointer manipulation.

Trigger Words

When you see these in a problem, think Linked List:

reverse linked list linked-list merge two sorted lists linked list cycle reorder list remove nth node from end of list copy list with random pointer merge k sorted lists reverse nodes in k-group

Template Code

def reverseList(head: ListNode) -> ListNode:
    prev = None
    curr = head
    
    while curr:
        next_temp = curr.next  # Save next
        curr.next = prev       # Reverse pointer
        prev = curr            # Move prev forward
        curr = next_temp       # Move curr forward
    
    return prev

Complexity

Typical Time	`O(n)`
Typical Space	`O(1)`

Common Variations

Basic Linked List
Linked List with constraints
Optimized Linked List

Practice Problems

Reverse Linked List medium Merge Two Sorted Lists medium Linked List Cycle medium Reorder List medium Remove Nth Node From End of List medium

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