Introduction to Programming in C

📘 Trees and Basic Tree Traversals in C (Preorder, Inorder, Postorder)

A tree is a non-linear hierarchical data structure. It is widely used in applications like parsing expressions, indexing databases, and organizing hierarchical data such as file systems.

🔹 Basic Terminology

• Root: The top node of the tree
• Leaf: A node with no children
• Parent: A node with one or more child nodes
• Subtree: A tree formed from a node and its descendants
• Depth: Number of edges from the root to the node

🔧 Defining a Binary Tree in C

struct Node {
  int data;
  struct Node* left;
  struct Node* right;
};

struct Node* createNode(int value) {
  struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
  newNode->data = value;
  newNode->left = newNode->right = NULL;
  return newNode;
}

🌿 Types of Binary Tree Traversals

Traversal means visiting all the nodes in a specific order. There are three common types:

1️⃣ Inorder Traversal (Left → Root → Right)

void inorder(struct Node* root) {
  if (root != NULL) {
    inorder(root->left);
    printf("%d ", root->data);
    inorder(root->right);
  }
}

2️⃣ Preorder Traversal (Root → Left → Right)

void preorder(struct Node* root) {
  if (root != NULL) {
    printf("%d ", root->data);
    preorder(root->left);
    preorder(root->right);
  }
}

3️⃣ Postorder Traversal (Left → Right → Root)

void postorder(struct Node* root) {
  if (root != NULL) {
    postorder(root->left);
    postorder(root->right);
    printf("%d ", root->data);
  }
}

📚 Real-Life Example (UdaanPath)

UdaanPath’s course structure could be visualized as a tree:

• Root: Programming in C
• Children: Variables, Functions, Pointers
• Leaves: Sub-topics like memory, syntax, examples

🧠 Applications of Tree Traversal

• Inorder: Expression evaluation (infix format)
• Preorder: Copying tree structure
• Postorder: Deleting or freeing the tree memory

📝 Practice Tasks

1. Create a binary tree and insert at least 5 nodes
2. Implement all three traversal methods
3. Print a tree using each traversal and analyze the order
4. Try drawing the tree structure based on traversal output

✅ Summary

• Trees store hierarchical data efficiently
• Traversals allow structured processing of tree data
• Inorder, Preorder, and Postorder are vital patterns

🚀 Coming Next

Next, we’ll move to Searching and Sorting Algorithms — core components for optimizing performance in C applications.