Here is the source code of the C program to search for an element in a tree iteratively. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

/*
* C Program to Traverse the Tree Non-Recursively
*/

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

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

void generate(struct node **, int);
int search(struct node *, int);
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. Search\n3. Exit\nChoice: ");
scanf("%d", &choice);
switch(choice)
{
case 1:
printf("Enter element to insert: ");
scanf("%d", &num);
generate(&head, num);
break;
case 2:
printf("Enter key to search: ");
scanf("%d", &key);
flag = search(head, key);
if (flag)
{
printf("Key found in tree\n");
}
else
{
printf("Key not found\n");
}
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)->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;
}
}
}

int search(struct node *head, int key)
{
while (head != NULL)
{
if (key > head->a)
{
head = head->right;
}
else if (key < head->a)
{
head = head->left;
}
else
{
return 1;
}
}
return 0;
}

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


$ cc pgm37.c
$ a.out

Enter your choice:
1. Insert
2. Search
3. Exit
Choice: 1
Enter element to insert: 1

Enter your choice:
1. Insert
2. Search
3. Exit
Choice: 1
Enter element to insert: 2

Enter your choice:
1. Insert
2. Search
3. Exit
Choice: 1
Enter element to insert: 3

Enter your choice:
1. Insert
2. Search
3. Exit
Choice: 1
Enter element to insert:
4

Enter your choice:
1. Insert
2. Search
3. Exit
Choice: 2
Enter key to search: 1
Key found in tree

Enter your choice:
1. Insert
2. Search
3. Exit
Choice: 2
Enter key to search: 6
Key not found

Enter your choice:
1. Insert
2. Search
3. Exit
Choice: 3
Memory Cleared
PROGRAM TERMINATED