programming-examples/c/Without_Recursion/C Program for Depth First Binary Tree Search without using Recursion.c

/*
 * C Program for Depth First Binary Tree Search without using
 * Recursion
 */
#include <stdio.h>
#include <stdlib.h>

struct node
{
    int a;
    struct node *left;
    struct node *right;
    int visited;
};

void generate(struct node **, int);
void DFS(struct node *);
void delete(struct node **);

int main()
{
    struct node *head = NULL;
    int choice = 0, num, flag = 0, key;
    do
        {
            printf("\nEnter your choice:\n1. Insert\n2. Perform DFS Traversal\n3. Exit\nChoice: ");
            scanf("%d", &choice);
            switch(choice)
                {
                case 1:
                    printf("Enter element to insert: ");
                    scanf("%d", &num);
                    generate(&head, num);
                    break;
                case 2:
                    DFS(head);
                    break;
                case 3:
                    delete(&head);
                    printf("Memory Cleared\nPROGRAM TERMINATED\n");
                    break;
                default:
                    printf("Not a valid input, try again\n");
                }
        }
    while (choice != 3);
    return 0;
}

void generate(struct node **head, int num)
{
    struct node *temp = *head, *prev = *head;
    if (*head == NULL)
        {
            *head = (struct node *)malloc(sizeof(struct node));
            (*head)->a = num;
            (*head)->visited = 0;
            (*head)->left = (*head)->right = NULL;
        }
    else
        {
            while (temp != NULL)
                {
                    if (num > temp->a)
                        {
                            prev = temp;
                            temp = temp->right;
                        }
                    else
                        {
                            prev = temp;
                            temp = temp->left;
                        }
                }
            temp = (struct node *)malloc(sizeof(struct node));
            temp->a = num;
            temp->visited = 0;
            if (temp->a >= prev->a)
                {
                    prev->right = temp;
                }
            else
                {
                    prev->left = temp;
                }
        }
}

void DFS(struct node *head)
{
    struct node *temp = head, *prev;
    printf("On DFS traversal we get:\n");
    while (temp && !temp->visited)
        {
            if (temp->left && !temp->left->visited)
                {
                    temp = temp->left;
                }
            else if (temp->right && !temp->right->visited)
                {
                    temp = temp->right;
                }
            else
                {
                    printf("%d  ", temp->a);
                    temp->visited = 1;
                    temp = head;
                }
        }
}

void delete(struct node **head)
{
    if (*head != NULL)
        {
            if ((*head)->left)
                {
                    delete(&(*head)->left);
                }
            if ((*head)->right)
                {
                    delete(&(*head)->right);
                }
            free(*head);
        }
}