Linked List Operation in C

linked_list.c

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

struct node{

	int data;
	struct node *next;

};

struct node *head=NULL;
int p,q,r,nodenumber,nodedata;

void main(){
	
	int operationtype,i;
	char nodeoperation;
	
	printf("Enter Number of Nodes you want to create:");
	
	scanf("%d",&nodenumber);
	
	for(i=1;i<=nodenumber;i++){
		printf("Enter %d Node data:",i);
		scanf("%d",&nodedata);
		createnode(nodedata);
	}
	
	printf("want to perfrom operation on node(y\\n)):");
	scanf("%s",&nodeoperation);
	if(nodeoperation=='y'||nodeoperation=='Y' ||nodeoperation=='yes'|| nodeoperation=='YES'){
		printf("1.Insert node at begning\n2.Insert node at position p(1>=p>=%d)\n3.Insert node at end\n4.Delete first node\n5.Delete position p  (1>=p>=%d) node\n6.Delete end node\n7.swap two nodes\n8.reverse list\n",nodenumber,nodenumber);
		printf("Choose position:");
		scanf("%d",&operationtype);
		switch(operationtype){
		
			case 1:
				printf("Enter data you want to insert:");
				scanf("%d",&nodedata);
				insert_at_begning(nodedata);
				break;
			case 2:
				printf("Enter position of node:");
				scanf("%d",&p);
				if(p==0){
					printf("Please enter position greater then 0\n");
					break;
				}else if(p>nodenumber){
					printf("Please enter correct position\n");
					break;
				}
				printf("Enter data you want to insert:");
				scanf("%d",&nodedata);
				insert_at_position_p(nodedata);
				break;
			case 3:
				printf("Enter data you want to insert:");
				scanf("%d",&nodedata);
				insert_at_end(nodedata);
				break;
			case 4:
				delete_first_node();
				break;
			case 5:
				printf("Enter position of node:");
				scanf("%d",&p);
				if(p==0){
					printf("Please enter position greater then 0\n");
					break;
				}else if(p>nodenumber){
					printf("Please enter correct position\n");
					break;
				}
				delete_p_node(p);
			case 6:
				delete_end_node();
				break;
			case 7:
				printf("Enter nodes you want to swap\n");
				scanf("%d %d",&p,&q);
				if(p==0||q==0){
					printf("Please enter position greater then 0\n");
					break;
				}else if(p>nodenumber||q>nodenumber){
					printf("Please enter correct position\n");
					break;
				}
				if(p>q){
					r=p;
					p=q;
					q=r;
				}
				swap_node(p,q);
				break;
			case 8:
				reverse_list();
				break;
				
			default:
				printf("Please enter correct position\n");
		
		
		}	
	
			
	
	}

	display();
}


void createnode(int x){

	struct node *newnode, *temp;
	
	newnode = (struct node*) malloc(sizeof(struct node));
	
	newnode->data=x;
	newnode->next=NULL;
	temp=head;
	
	if(temp==NULL){
	
		head=newnode;
	}else{
		while(temp->next!=NULL){
			
			temp=temp->next;
		
		}
		temp->next=newnode;
	}


}


void display(){
	
	struct node *temp;
	temp=head;
	printf("created node data are\n");
	while(temp->next!=NULL){
		
		printf("%d\n",temp->data);
		temp=temp->next;
	
	}
	printf("%d\n",temp->data);

}


void insert_at_begning(int x){

	struct node *newnode;
	
	newnode=(struct node*) malloc(sizeof(struct node));
	
	newnode->data=x;
	newnode->next=head;
	head=newnode;
}

void insert_at_position_p(int x){

	if(p>1){
		struct node *newnode, *temp;
		int i;
	
		newnode=(struct node*)malloc(sizeof(struct node));
	
		newnode->data=x;
		temp=head;
		for(i=1;i<p-1;i++){
	
			temp=temp->next;
	
		}
		newnode->next=temp->next;
		temp->next=newnode;
	} else if(p==1){
		insert_at_begning(nodedata);
	}
}

void insert_at_end(int x){

	struct node *newnode, *temp;
	
	newnode=(struct node*)malloc(sizeof(struct node));
	
	newnode->data=x;
	newnode->next=NULL;
	
	temp=head;
	
	while(temp->next!=NULL){
		
		temp=temp->next;
	}
	temp->next=newnode;
}

void delete_first_node(){

	struct node *temp;
	
	temp=head;
	head=head->next;
	free(temp);
}

void delete_p_node(int x){

	if(p!=1){
		struct node *temp,*q;
		int i;
	
		temp=head;
	
		for(i=1;i<p-1;i++){
			temp=temp->next;
		}
		q=temp->next;
		temp->next=temp->next->next;
		free(q);
	}else if(p==1){
		delete_first_node();
	}
}

void delete_end_node(){

	if(head->next!=NULL){
		struct node *temp,*q;
		temp=head;
		while(temp->next->next!=NULL){
			temp=temp->next;
		}
		q=temp->next;
		temp->next=temp->next->next;
		free(q);
	}else{
		free(head);
	}
}

void swap_node(int x , int y){

	struct node *temp1,*temp2;
	int s,i;
	
	temp1=temp2=head;
	
	for(i=1;i<p;i++){
		temp1=temp1->next;
	}
	for(i=1;i<q;i++){
		temp2=temp2->next;
	}
	
	s=temp1->data;
	temp1->data=temp2->data;
	temp2->data=s;
}

void reverse_list(){
	
	struct node *nextnode=NULL,*prev=NULL;
	while(head->next){
		
		nextnode=head->next;
		head->next=prev;
		prev=head;
		head=nextnode;
	}
	head->next=prev;

}