programming-examples/c/Recursion/C Program to Traverse the Tree Recursively.c

/*
 * C Program to Traverse the Tree Recursively
 */
#include <stdio.h>
#include <stdlib.h>

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

void generate(struct node **, int);
void infix(struct node *);
void postfix(struct node *);
void prefix(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. Traverse via infix\n3.Traverse via prefix\n4. Traverse via postfix\n5. Exit\nChoice: ");
            scanf("%d", &choice);
            switch(choice)
                {
                case 1:
                    printf("Enter element to insert: ");
                    scanf("%d", &num);
                    generate(&head, num);
                    break;
                case 2:
                    infix(head);
                    break;
                case 3:
                    prefix(head);
                    break;
                case 4:
                    postfix(head);
                    break;
                case 5:
                    delete(&head);
                    printf("Memory Cleared\nPROGRAM TERMINATED\n");
                    break;
                default:
                    printf("Not a valid input, try again\n");
                }
        }
    while (choice != 5);
    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)->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;
            if (num >= prev->a)
                {
                    prev->right = temp;
                }
            else
                {
                    prev->left = temp;
                }
        }
}

void infix(struct node *head)
{
    if (head)
        {
            infix(head->left);
            printf("%d   ", head->a);
            infix(head->right);
        }
}

void prefix(struct node *head)
{
    if (head)
        {
            printf("%d   ", head->a);
            prefix(head->left);
            prefix(head->right);
        }
}

void postfix(struct node *head)
{
    if (head)
        {
            postfix(head->left);
            postfix(head->right);
            printf("%d   ", head->a);
        }
}

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