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Advanced Data Structures

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In this module, we will delve into advanced data structures in RPG programming. Understanding these structures will allow you to handle complex data more efficiently and write more robust programs. We will cover the following topics:

  1. Introduction to Advanced Data Structures
  2. Linked Lists
  3. Stacks and Queues
  4. Trees and Graphs
  5. Practical Examples and Exercises

  1. Introduction to Advanced Data Structures

Advanced data structures are essential for managing and organizing data efficiently. They provide ways to store and manipulate data that go beyond simple arrays and lists. Here are some key concepts:

  • Dynamic Memory Allocation: Unlike static arrays, advanced data structures often require dynamic memory allocation.
  • Pointers: Pointers are used to link elements in structures like linked lists and trees.
  • Complexity: Understanding the time and space complexity of operations on these structures is crucial for performance optimization.

  1. Linked Lists

A linked list is a linear data structure where each element (node) contains a reference (link) to the next element in the sequence. There are several types of linked lists:

  • Singly Linked List: Each node points to the next node.
  • Doubly Linked List: Each node points to both the next and the previous node.
  • Circular Linked List: The last node points back to the first node.

Example: Singly Linked List

DCL-S NodePointer POINTER;
DCL-DS Node;
  Value INT(10);
  Next POINTER;
END-DS;

DCL-S Head POINTER;
DCL-S Temp POINTER;

// Function to create a new node
DCL-PROC CreateNode;
  DCL-PI *N POINTER;
  DCL-PARM Value INT(10);
  DCL-S NewNode POINTER;
  ALLOC NewNode;
  NewNode->Value = Value;
  NewNode->Next = *NULL;
  RETURN NewNode;
END-PROC;

// Function to insert a node at the beginning
DCL-PROC InsertAtBeginning;
  DCL-PI *N POINTER;
  DCL-PARM Head POINTER;
  DCL-PARM Value INT(10);
  DCL-S NewNode POINTER;
  NewNode = CreateNode(Value);
  NewNode->Next = Head;
  Head = NewNode;
  RETURN Head;
END-PROC;

Explanation

  • Node Structure: Defines a node with a value and a pointer to the next node.
  • CreateNode Function: Allocates memory for a new node and initializes it.
  • InsertAtBeginning Function: Inserts a new node at the beginning of the list.

  1. Stacks and Queues

Stacks and queues are abstract data types that follow specific order principles:

  • Stack: Follows Last In, First Out (LIFO) principle.
  • Queue: Follows First In, First Out (FIFO) principle.

Example: Stack Implementation

DCL-DS StackNode;
  Value INT(10);
  Next POINTER;
END-DS;

DCL-S StackTop POINTER;

// Function to push an element onto the stack
DCL-PROC Push;
  DCL-PI *N POINTER;
  DCL-PARM StackTop POINTER;
  DCL-PARM Value INT(10);
  DCL-S NewNode POINTER;
  NewNode = CreateNode(Value);
  NewNode->Next = StackTop;
  StackTop = NewNode;
  RETURN StackTop;
END-PROC;

// Function to pop an element from the stack
DCL-PROC Pop;
  DCL-PI INT(10);
  DCL-PARM StackTop POINTER;
  DCL-S Temp POINTER;
  DCL-S Value INT(10);
  IF StackTop <> *NULL;
    Temp = StackTop;
    Value = StackTop->Value;
    StackTop = StackTop->Next;
    DEALLOC Temp;
  ELSE;
    Value = -1; // Stack is empty
  ENDIF;
  RETURN Value;
END-PROC;

Explanation

  • Push Function: Adds an element to the top of the stack.
  • Pop Function: Removes and returns the top element of the stack.

  1. Trees and Graphs

Trees and graphs are hierarchical data structures:

  • Tree: A collection of nodes with a parent-child relationship.
  • Graph: A collection of nodes connected by edges, which can be directed or undirected.

Example: Binary Tree Node

DCL-DS TreeNode;
  Value INT(10);
  Left POINTER;
  Right POINTER;
END-DS;

DCL-S Root POINTER;

// Function to insert a node in a binary tree
DCL-PROC InsertNode;
  DCL-PI *N POINTER;
  DCL-PARM Root POINTER;
  DCL-PARM Value INT(10);
  IF Root = *NULL;
    Root = CreateNode(Value);
  ELSEIF Value < Root->Value;
    Root->Left = InsertNode(Root->Left: Value);
  ELSE;
    Root->Right = InsertNode(Root->Right: Value);
  ENDIF;
  RETURN Root;
END-PROC;

Explanation

  • TreeNode Structure: Defines a node with a value and pointers to left and right children.
  • InsertNode Function: Recursively inserts a node into the binary tree.

  1. Practical Examples and Exercises

Exercise 1: Implement a Doubly Linked List

Task: Implement a doubly linked list with functions to insert and delete nodes.

Exercise 2: Implement a Queue

Task: Implement a queue using linked lists with enqueue and dequeue operations.

Exercise 3: Binary Search Tree

Task: Implement a binary search tree with functions to insert, delete, and search for nodes.

Solutions

Solution 1: Doubly Linked List

DCL-DS DoublyNode;
  Value INT(10);
  Prev POINTER;
  Next POINTER;
END-DS;

DCL-S Head POINTER;
DCL-S Tail POINTER;

// Function to insert a node at the end
DCL-PROC InsertAtEnd;
  DCL-PI *N POINTER;
  DCL-PARM Head POINTER;
  DCL-PARM Tail POINTER;
  DCL-PARM Value INT(10);
  DCL-S NewNode POINTER;
  NewNode = CreateNode(Value);
  IF Head = *NULL;
    Head = NewNode;
    Tail = NewNode;
  ELSE;
    Tail->Next = NewNode;
    NewNode->Prev = Tail;
    Tail = NewNode;
  ENDIF;
  RETURN Head;
END-PROC;

Solution 2: Queue

DCL-DS QueueNode;
  Value INT(10);
  Next POINTER;
END-DS;

DCL-S Front POINTER;
DCL-S Rear POINTER;

// Function to enqueue an element
DCL-PROC Enqueue;
  DCL-PI *N POINTER;
  DCL-PARM Rear POINTER;
  DCL-PARM Value INT(10);
  DCL-S NewNode POINTER;
  NewNode = CreateNode(Value);
  IF Rear = *NULL;
    Front = NewNode;
    Rear = NewNode;
  ELSE;
    Rear->Next = NewNode;
    Rear = NewNode;
  ENDIF;
  RETURN Rear;
END-PROC;

// Function to dequeue an element
DCL-PROC Dequeue;
  DCL-PI INT(10);
  DCL-PARM Front POINTER;
  DCL-S Temp POINTER;
  DCL-S Value INT(10);
  IF Front <> *NULL;
    Temp = Front;
    Value = Front->Value;
    Front = Front->Next;
    DEALLOC Temp;
  ELSE;
    Value = -1; // Queue is empty
  ENDIF;
  RETURN Value;
END-PROC;

Solution 3: Binary Search Tree

DCL-DS BSTNode;
  Value INT(10);
  Left POINTER;
  Right POINTER;
END-DS;

DCL-S Root POINTER;

// Function to search for a node
DCL-PROC SearchNode;
  DCL-PI *N POINTER;
  DCL-PARM Root POINTER;
  DCL-PARM Value INT(10);
  IF Root = *NULL OR Root->Value = Value;
    RETURN Root;
  ELSEIF Value < Root->Value;
    RETURN SearchNode(Root->Left: Value);
  ELSE;
    RETURN SearchNode(Root->Right: Value);
  ENDIF;
END-PROC;

Conclusion

In this module, we explored advanced data structures such as linked lists, stacks, queues, and trees. These structures are fundamental for efficient data management and manipulation in RPG programming. By understanding and implementing these structures, you can write more efficient and robust programs. In the next module, we will delve into RPG IV and explore its advanced features.

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