C Program to Implement Create and Display Operation for a Binary Tree

A Binary Tree is a hierarchical data structure where each node can have at most two children: a left child and a right child. In this program, we will implement create and display operations for a binary tree in a simple, student-friendly way.

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📝 Problem Statement

Q1. A) Write C programs to implement create and display operation for binary tree.

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💡 Logic (Student-Friendly Steps)

🔹 Create Operation

1. Define a structure for a node containing:
   • data
   • left pointer
   • right pointer
2. Create a function to dynamically allocate a new node.
3. Manually link nodes or accept input from the user to build the tree.

🔹 Display Operation

1. Use a recursive function to traverse the tree.
2. We can use Preorder Traversal (Root → Left → Right) to display nodes.

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💻 Source Code (Simple Version)

#include <stdio.h>
#include <stdlib.h>

// Node structure
struct node
{
    int data;
    struct node *left;
    struct node *right;
};

// Function to create a new node
struct node* createNode(int value)
{
    struct node* newnode = (struct node*)malloc(sizeof(struct node));
    newnode->data = value;
    newnode->left = NULL;
    newnode->right = NULL;
    return newnode;
}

// Function to display tree (Preorder Traversal)
void displayTree(struct node* root)
{
    if(root == NULL)
        return;

    printf("%d ", root->data);    // Visit root
    displayTree(root->left);      // Traverse left subtree
    displayTree(root->right);     // Traverse right subtree
}

int main()
{
    struct node* root = NULL;
    int n, value, i;

    printf("Enter number of nodes: ");
    scanf("%d", &n);

    if(n <= 0)
    {
        printf("Tree cannot be created.\n");
        return 0;
    }

    // Create root node
    printf("Enter value for root node: ");
    scanf("%d", &value);
    root = createNode(value);

    // Insert remaining nodes manually (for simplicity)
    struct node* temp;
    for(i = 1; i < n; i++)
    {
        printf("Enter value for node %d: ", i+1);
        scanf("%d", &value);
        struct node* newnode = createNode(value);

        temp = root;
        while(1)
        {
            if(temp->left == NULL)
            {
                temp->left = newnode;
                break;
            }
            else if(temp->right == NULL)
            {
                temp->right = newnode;
                break;
            }
            else
            {
                temp = temp->left;  // Move to left for next insertion
            }
        }
    }

    printf("Binary Tree nodes (Preorder Traversal):\n");
    displayTree(root);

    return 0;
}

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🖥️ Sample Output

Enter number of nodes: 5
Enter value for root node: 10
Enter value for node 2: 20
Enter value for node 3: 30
Enter value for node 4: 40
Enter value for node 5: 50
Binary Tree nodes (Preorder Traversal):
10 20 40 50 30

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🎓 Viva Questions with Answers

1. What is a binary tree?

A tree in which each node has at most two children: left and right.

2. What is the root node?

The first node of the tree, which acts as the starting point.

3. What is a leaf node?

A node with no left or right children.

4. What is preorder traversal?

Visiting Root → Left → Right recursively.

5. How do you insert a new node in a binary tree?

By creating a node and linking it to the first available left or right child in a simple implementation.