doubly linked list: #2 Alokasi memori dan membuat node

doubly linked list #2: Memory allocation and creating nodes

What this tutorial covers

• Purpose: show how to allocate memory for nodes and create a node-construction function for a linked list (preparation for insert operations covered in the next video).
• Context: second video in a series (previous video introduced basics; next video will cover Insert First).

Key technical concepts explained

Dynamic allocation

• Use new (C++/similar) to create node objects in heap memory so they persist beyond the allocating function’s scope.

Node structure fields

• Typical fields in a doubly linked-list node:
  • data — value stored in the node
  • prev — pointer to the previous node
  • next — pointer to the next node

Allocation function pattern

• Create a function (e.g., allocate or allocation) that:
  • takes data as a parameter
  • returns a pointer/address to a newly created node
• Inside the function:
  • allocate a new node
  • set node->prev = NULL
  • set node->next = NULL
  • set node->data = value
  • return the node address

Example (C++-style pseudocode):

Node* allocate(int value) {
    Node* node = new Node;
    node->prev = NULL;
    node->next = NULL;
    node->data = value;
    return node;
}

Using the allocation function

• Calling the allocation function with values (e.g., 20, 30, 40) creates separate nodes in memory.
• If only the last returned pointer is stored, earlier nodes still exist but their addresses are lost and they cannot be accessed (memory leak).

Pointer semantics and access

• Storing only the most recent pointer means earlier nodes are unreachable.
• Printing from the single stored pointer will show only the last node’s data (for example, 40).
• To access multiple nodes you must:
  • connect them by setting next/prev pointers
  • maintain a head pointer that points to the first node

Demonstration details and troubleshooting

• The instructor demonstrates allocating multiple nodes and shows that the printed result is the last node’s value when only the last pointer is stored.
• An error occurred during the demo due to a wrong method name; it was corrected and the code rerun.
• The instructor emphasizes the importance of returning and storing node addresses from the allocation function so nodes remain accessible.

Upcoming / related topics

• Next video will show insertion methods (Insert First) and how to connect nodes to form the list.

Main speaker / source

• The video presenter / tutorial host (unnamed YouTube channel author).