Linked Lists

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Introduction to linked list

A linked list is a linear data structure where each element is a separate object.
Linked list elements are not stored at contiguous location; the elements are linked using pointers.

Each node of a list is made up of two items - the data and a reference to the next node. The last node has a reference to null. The entry point into a linked list is called the head of the list. It should be noted that head is not a separate node, but the reference to the first node. If the list is empty then the head is a null reference.

 
Linked List Representation
 
An example of a linked list node with an integer data.
// Linked list example in C/C++
// A linked list node
struct ListNode
{
  int val;
  struct ListNode *next;
};
// Linked list example in Java
// Linked list class
class ListNode
{
    // head of list
    Node head;
 
    // Node class
    class Node
    {
        int val;
        Node next;
          
        // Constructor to create a new node
        Node(int v) {
           val = v;
        }
    }
}
# Linked list example in Python
# Node class
class Node:
    # Function to initialize the node object
    def __init__(self, v):
        self.val = v  # Assign value
        self.next = None  # Initialize next as null
  
# Linked List class
class ListNode:
    # Function to initialize the Linked List
    def __init__(self): 
        self.head = None

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Linked Lists Problems

List sort
Problem Score Companies Time Status
Sort Binary Linked List 200 33:21
Partition List 275
49:36
Insertion Sort List 300
49:25
Sort List 350 59:53
Pointer move
Problem Score Companies Time Status
K reverse linked list 200 60:30
Even Reverse 200 45:58
Swap List Nodes in pairs 350 33:34
Rotate List 350 33:58
List trick
Problem Score Companies Time Status
Kth Node From Middle 200 30:12
Reverse Alternate K Nodes 300 54:08
Reverse Link List II 450 57:24
Reorder List 600 57:10
List math
Problem Score Companies Time Status
Add Two Numbers as Lists 250 43:07
List Cycle 600 39:15
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