Tree Traversal.c

#include <stdio.h>


struct node
{
    int data;

    struct node *leftChild;
    struct node *rightChild;
};

struct node *root = NULL;

void insert(int data)
{
    struct node *tempNode = (struct node*) malloc(sizeof(struct node));
    struct node *current;
    struct node *parent;

    tempNode->data = data;
    tempNode->leftChild = NULL;
    tempNode->rightChild = NULL;


    if(root == NULL)
    {
        root = tempNode;
    }
    else
    {
        current = root;
        parent = NULL;

        while(1)
        {
            parent = current;


            if(data < parent->data)
            {
                current = current->leftChild;


                if(current == NULL)
                {
                    parent->leftChild = tempNode;
                    return;
                }
            }
            else
            {
                current = current->rightChild;


                if(current == NULL)
                {
                    parent->rightChild = tempNode;
                    return;
                }
            }
        }
    }
}

struct node* search(int data)
{
    struct node *current = root;
    printf("Visiting elements: ");

    while(current->data != data)
    {
        if(current != NULL)
            printf("%d ",current->data);


        if(current->data > data)
        {
            current = current->leftChild;
        }

        else
        {
            current = current->rightChild;
        }


        if(current == NULL)
        {
            return NULL;
        }
    }

    return current;
}

void pre_order_traversal(struct node* root)
{
    if(root != NULL)
    {
        printf("%d ",root->data);
        pre_order_traversal(root->leftChild);
        pre_order_traversal(root->rightChild);
    }
}

void inorder_traversal(struct node* root)
{
    if(root != NULL)
    {
        inorder_traversal(root->leftChild);
        printf("%d ",root->data);
        inorder_traversal(root->rightChild);
    }
}

void post_order_traversal(struct node* root)
{
    if(root != NULL)
    {
        post_order_traversal(root->leftChild);
        post_order_traversal(root->rightChild);
        printf("%d ", root->data);
    }
}

int main()
{
    int i;
    int array[7] = { 27, 14, 35, 10, 19, 31, 42 };

    for(i = 0; i < 7; i++)
        insert(array[i]);

    i = 31;
    struct node * temp = search(i);

    if(temp != NULL)
    {
        printf("[%d] Element found.", temp->data);
        printf("\n");
    }
    else
    {
        printf("[ x ] Element not found (%d).\n", i);
    }

    i = 15;
    temp = search(i);

    if(temp != NULL)
    {
        printf("[%d] Element found.", temp->data);
        printf("\n");
    }
    else
    {
        printf("[ x ] Element not found (%d).\n", i);
    }

    printf("\nPreorder traversal: ");
    pre_order_traversal(root);

    printf("\nInorder traversal: ");
    inorder_traversal(root);

    printf("\nPost order traversal: ");
    post_order_traversal(root);

    return 0;
}