TheAlgorithms-C/data_structures/linked_list/middleElementInList.c

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

/* Link list node */
struct Node 
{ 
	int data; 
	struct Node* next; 
}; 

/* Function to get the middle of the linked list*/
void printMiddle(struct Node *head) 
{ 
	struct Node *slow_ptr = head; 
	struct Node *fast_ptr = head; 

	if (head!=NULL) 
	{ 
		while (fast_ptr != NULL && fast_ptr->next != NULL) 
		{ 
			fast_ptr = fast_ptr->next->next; 
			slow_ptr = slow_ptr->next; 
		} 
		printf("The middle element is [%d]\n\n", slow_ptr->data); 
	} 
} 

void push(struct Node** head_ref, int new_data) 
{ 
	/* allocate node */
	struct Node* new_node = 
		(struct Node*) malloc(sizeof(struct Node)); 

	/* put in the data */
	new_node->data = new_data; 

	/* link the old list off the new node */
	new_node->next = (*head_ref); 

	/* move the head to point to the new node */
	(*head_ref) = new_node; 
} 

// A utility function to print a given linked list 
void printList(struct Node *ptr) 
{ 
	while (ptr != NULL) 
	{ 
		printf("%d->", ptr->data); 
		ptr = ptr->next; 
	} 
	printf("NULL\n"); 
} 

/* Drier program to test above function*/
int main() 
{ 
	/* Start with the empty list */
	struct Node* head = NULL; 
	int i; 

	for (i=5; i>0; i--) 
	{ 
		push(&head, i); 
		printList(head); 
		printMiddle(head); 
	} 

	return 0; 
}