# Insertion in Unrolled Linked List

An unrolled linked list is a linked list of small arrays, all of the same size where each is so small that the insertion or deletion is fast and quick, but large enough to fill the cache line. An iterator pointing into the list consists of both a pointer to a node and an index into that node containing an array. It is also a data structure and is another variant of Linked List. It is related to B-Tree. It can store an array of elements at a node unlike a normal linked list which stores single element at a node. It is combination of arrays and linked list fusion-ed into one. It increases cache performance and decreases the memory overhead associated with storing reference for metadata. Other major advantages and disadvantages are already mentioned in the previous article.

Prerequisite : Introduction to Unrolled Linked List

Below is the insertion and display operation of Unrolled Linked List.

```Input : 72 76 80 94 90 70
capacity = 3
Output : Unrolled Linked List :
72 76
80 94
90 70
Explanation : The working is well shown in the
algorithm below. The nodes get broken at the
mentioned capacity i.e., 3 here, when 3rd element
is entered, the flow moves to another newly created
node. Every node contains an array of size
(int)[(capacity / 2) + 1]. Here it is 2.

Input : 49 47 62 51 77 17 71 71 35 76 36 54
capacity = 5
Output :
49 47 62
51 77 17
71 71 35
76 36 54
Explanation : The working is well shown in the
algorithm below. The nodes get broken at the
mentioned capacity i.e., 5 here, when 5th element
is entered, the flow moves to another newly
created node. Every node contains an array of
size (int)[(capacity / 2) + 1]. Here it is 3.
```

Algorithm :

```Insert (ElementToBeInserted)
if start_pos == NULL
Insert the first element into the first node
start_pos.numElement ++
end_pos = start_pos
If end_pos.numElements + 1 <  node_size
end_pos.numElements.push(newElement)
end_pos.numElements ++
else
create a new Node new_node
move final half of end_pos.data into new_node.data
new_node.data.push(newElement)
end_pos.numElements = end_pos.data.size / 2 + 1
end_pos.next = new_node
end_pos = new_node
```

Following is the Java implementation of the insertion and display operation. In the below code, the capacity is 5 and random numbers are input.

 `/* Java program to show the insertion operation ` `* of Unrolled Linked List */` `import` `java.util.Scanner; ` `import` `java.util.Random; ` ` `  `// class for each node ` `class` `UnrollNode { ` `    ``UnrollNode next; ` `    ``int` `num_elements; ` `    ``int` `array[]; ` ` `  `    ``// Constructor ` `    ``public` `UnrollNode(``int` `n) ` `    ``{ ` `        ``next = ``null``; ` `        ``num_elements = ``0``; ` `        ``array = ``new` `int``[n]; ` `    ``} ` `} ` ` `  `// Operation of Unrolled Function ` `class` `UnrollLinkList { ` ` `  `    ``private` `UnrollNode start_pos; ` `    ``private` `UnrollNode end_pos; ` ` `  `    ``int` `size_node; ` `    ``int` `nNode; ` ` `  `    ``// Parameterized Constructor ` `    ``UnrollLinkList(``int` `capacity) ` `    ``{ ` `        ``start_pos = ``null``; ` `        ``end_pos = ``null``; ` `        ``nNode = ``0``; ` `        ``size_node = capacity + ``1``; ` `    ``} ` ` `  `    ``// Insertion operation ` `    ``void` `Insert(``int` `num) ` `    ``{ ` `        ``nNode++; ` ` `  `        ``// Check if the list starts from NULL ` `        ``if` `(start_pos == ``null``) { ` `            ``start_pos = ``new` `UnrollNode(size_node); ` `            ``start_pos.array[``0``] = num; ` `            ``start_pos.num_elements++; ` `            ``end_pos = start_pos; ` `            ``return``; ` `        ``} ` ` `  `        ``// Attaching the elements into nodes ` `        ``if` `(end_pos.num_elements + ``1` `< size_node) { ` `            ``end_pos.array[end_pos.num_elements] = num; ` `            ``end_pos.num_elements++; ` `        ``} ` ` `  `        ``// Creation of new Node ` `        ``else` `{ ` `            ``UnrollNode node_pointer = ``new` `UnrollNode(size_node); ` `            ``int` `j = ``0``; ` `            ``for` `(``int` `i = end_pos.num_elements / ``2` `+ ``1``; ` `                 ``i < end_pos.num_elements; i++) ` `                ``node_pointer.array[j++] = end_pos.array[i]; ` ` `  `            ``node_pointer.array[j++] = num; ` `            ``node_pointer.num_elements = j; ` `            ``end_pos.num_elements = end_pos.num_elements / ``2` `+ ``1``; ` `            ``end_pos.next = node_pointer; ` `            ``end_pos = node_pointer; ` `        ``} ` `    ``} ` ` `  `    ``// Display the Linked List ` `    ``void` `display() ` `    ``{ ` `        ``System.out.print(``"\nUnrolled Linked List = "``); ` `        ``System.out.println(); ` `        ``UnrollNode pointer = start_pos; ` `        ``while` `(pointer != ``null``) { ` `            ``for` `(``int` `i = ``0``; i < pointer.num_elements; i++) ` `                ``System.out.print(pointer.array[i] + ``" "``); ` `            ``System.out.println(); ` `            ``pointer = pointer.next; ` `        ``} ` `        ``System.out.println(); ` `    ``} ` `} ` ` `  `/* Main Class */` `class` `UnrolledLinkedList_Check { ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `main(String args[]) ` `    ``{ ` `        ``Scanner sc = ``new` `Scanner(System.in); ` ` `  `        ``// create instance of Random class ` `        ``Random rand = ``new` `Random(); ` ` `  `        ``UnrollLinkList ull = ``new` `UnrollLinkList(``5``); ` ` `  `        ``// Perform Insertion Operation ` `        ``for` `(``int` `i = ``0``; i < ``12``; i++) { ` ` `  `            ``// Generate random integers in range 0 to 99 ` `            ``int` `rand_int1 = rand.nextInt(``100``); ` `            ``System.out.println(``"Entered Element is "` `+ rand_int1); ` `            ``ull.Insert(rand_int1); ` `            ``ull.display(); ` `        ``} ` `    ``} ` `} `

 `/* C# program to show the insertion operation ` `* of Unrolled Linked List */` `using` `System; ` ` `  `// class for each node ` `public` `class` `UnrollNode { ` `    ``public` `UnrollNode next; ` `    ``public` `int` `num_elements; ` `    ``public` `int``[] array; ` ` `  `    ``// Constructor ` `    ``public` `UnrollNode(``int` `n) ` `    ``{ ` `        ``next = ``null``; ` `        ``num_elements = 0; ` `        ``array = ``new` `int``[n]; ` `    ``} ` `} ` ` `  `// Operation of Unrolled Function ` `public` `class` `UnrollLinkList { ` ` `  `    ``private` `UnrollNode start_pos; ` `    ``private` `UnrollNode end_pos; ` ` `  `    ``int` `size_node; ` `    ``int` `nNode; ` ` `  `    ``// Parameterized Constructor ` `    ``public` `UnrollLinkList(``int` `capacity) ` `    ``{ ` `        ``start_pos = ``null``; ` `        ``end_pos = ``null``; ` `        ``nNode = 0; ` `        ``size_node = capacity + 1; ` `    ``} ` ` `  `    ``// Insertion operation ` `    ``public` `void` `Insert(``int` `num) ` `    ``{ ` `        ``nNode++; ` ` `  `        ``// Check if the list starts from NULL ` `        ``if` `(start_pos == ``null``) { ` `            ``start_pos = ``new` `UnrollNode(size_node); ` `            ``start_pos.array[0] = num; ` `            ``start_pos.num_elements++; ` `            ``end_pos = start_pos; ` `            ``return``; ` `        ``} ` ` `  `        ``// Attaching the elements into nodes ` `        ``if` `(end_pos.num_elements + 1 < size_node) { ` `            ``end_pos.array[end_pos.num_elements] = num; ` `            ``end_pos.num_elements++; ` `        ``} ` ` `  `        ``// Creation of new Node ` `        ``else` `{ ` `            ``UnrollNode node_pointer = ``new` `UnrollNode(size_node); ` `            ``int` `j = 0; ` `            ``for` `(``int` `i = end_pos.num_elements / 2 + 1; ` `                 ``i < end_pos.num_elements; i++) ` `                ``node_pointer.array[j++] = end_pos.array[i]; ` ` `  `            ``node_pointer.array[j++] = num; ` `            ``node_pointer.num_elements = j; ` `            ``end_pos.num_elements = end_pos.num_elements / 2 + 1; ` `            ``end_pos.next = node_pointer; ` `            ``end_pos = node_pointer; ` `        ``} ` `    ``} ` ` `  `    ``// Display the Linked List ` `    ``public` `void` `display() ` `    ``{ ` `        ``Console.Write(``"\nUnrolled Linked List = "``); ` `        ``Console.WriteLine(); ` `        ``UnrollNode pointer = start_pos; ` `        ``while` `(pointer != ``null``) { ` `            ``for` `(``int` `i = 0; i < pointer.num_elements; i++) ` `                ``Console.Write(pointer.array[i] + ``" "``); ` `            ``Console.WriteLine(); ` `            ``pointer = pointer.next; ` `        ``} ` `        ``Console.WriteLine(); ` `    ``} ` `} ` ` `  `/* Main Class */` `public` `class` `UnrolledLinkedList_Check { ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `Main(String[] args) ` `    ``{ ` `        ``// create instance of Random class ` `        ``Random rand = ``new` `Random(); ` ` `  `        ``UnrollLinkList ull = ``new` `UnrollLinkList(5); ` ` `  `        ``// Perform Insertion Operation ` `        ``for` `(``int` `i = 0; i < 12; i++) { ` ` `  `            ``// Generate random integers in range 0 to 99 ` `            ``int` `rand_int1 = rand.Next(100); ` `            ``Console.WriteLine(``"Entered Element is "` `+ rand_int1); ` `            ``ull.Insert(rand_int1); ` `            ``ull.display(); ` `        ``} ` `    ``} ` `} ` ` `  `// This code has been contributed by 29AjayKumar `

Output:
```Entered Element is 90

90

Entered Element is 3

90 3

Entered Element is 12

90 3 12

Entered Element is 43

90 3 12 43

Entered Element is 88

90 3 12 43 88

Entered Element is 94

90 3 12
43 88 94

Entered Element is 15

90 3 12
43 88 94 15

Entered Element is 7

90 3 12
43 88 94 15 7

Entered Element is 67

90 3 12
43 88 94
15 7 67

Entered Element is 74

90 3 12
43 88 94
15 7 67 74

Entered Element is 85

90 3 12
43 88 94
15 7 67 74 85

Entered Element is 48

90 3 12
43 88 94
15 7 67
74 85 48
```

Time complexity : O(n)
Also, few real world applications :

• It is used in B-Tree and T-Tree
• Used in Hashed Array Tree
• Used in Skip List
• Used in CDR Coding

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Improved By : 29AjayKumar

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