08searchFirstOcc.c

#include<stdio.h>
#include<stdlib.h>
struct node{
	int data;
	struct node *next;
};
int count(struct node **head);
int insertLast(struct node **head,int no);
int insertFirst(struct node **head,int no);
int deleteFirst(struct node **head);
int deleteLast(struct node **head);
int deleteAtPos(struct node **head,int pos);
int insertAtPos(struct node **head,int no,int pos);
int searchFirstOcc(struct node *head,int no);
int searchLastOcc(struct node *head,int no);
void displayLL(struct node**);
int main(){
	struct node *head=NULL;
	int itr1,num,no,pos;
	printf("Enter number of nodes to be created.\n");
	scanf("%d",&num);
	for(itr1=1;itr1<=num;itr1++){
		printf("Enter data of node %d.\n",itr1);
		scanf(" %d",&no);
		insertLast(&head,no);
	}
	displayLL(&head);
	printf("Enter element to be searched.\n");
	scanf(" %d",&pos);
	searchLastOcc(head,pos);
	displayLL(&head);
	free(head);
	return 0;
}

int searchFirstOcc(struct node *head,int no){
	struct node *temp=head;
	int cnt=1;
	while(temp->data!=no){
		if(temp->next==NULL){
			break;
		}
		cnt++;
		temp=temp->next;
	}	
	if(temp->data==no){
		printf("First Occurence of %d is : %d\n",no,cnt);
		return 0;
	}else{
		printf("Element not present in list.\n");
		return 1;
	}
}
int searchLastOcc(struct node *head,int no){
	struct node *temp=head;
	int cnt,cnt1;
	cnt=count(&head);
	int itr1=0,arr[cnt];
	while(temp->next!=NULL){
		arr[itr1]=temp->data;
		itr1++;
		temp=temp->next;
	}
	arr[itr1]=temp->data;
	cnt1=cnt-1;
	for(itr1=cnt1;itr1>=0;itr1--){
		if(arr[itr1]==no){
			printf("Last Occ of %d is %d\n",no,cnt);
			break;
		}
		cnt--;
	}
	return 0;
}
int deleteFirst(struct node **head){
	struct node *temp=*head;
	if(*head==NULL){
		printf("nothing to delete.\n");
	}else if((*head)->next==NULL){
		free(temp);
		*head=NULL;
	}else{
		*head=temp->next;
		free(temp);
	}
	return 0;
}
int deleteLast(struct node **head){
	struct node *temp=*head;
	struct node *temp1=*head;
	if(*head==NULL){
		printf("Nothing to delete.\n");
	}else if((*head)->next==NULL){
		free(temp);
		head=NULL;
	}else{
		while(temp->next!=NULL){
			temp=temp->next;
		}
		while(temp1->next!=temp){
			temp1=temp1->next;
		}
		temp1->next=NULL;
		free(temp);
		temp=NULL;
	}
	return 0;
}
int deleteAtPos(struct node **head,int pos){
	int cnt;
	struct node *temp=*head,*temp1;
	cnt=count(head);
	if(*head==NULL){
		printf("Nothing to delete.\n");
	}else if(pos==1){
		deleteFirst(head);
	}else if(cnt==pos){
		deleteLast(head);
	}else{
		while(pos-1>1){
			temp=temp->next;
			pos--;
		}
		temp1=temp->next;
		temp->next=temp1->next;
		free(temp1);
	}
	return 0;
}	
int count(struct node **head){
	int cnt=1;
	struct node *temp=*head;
	while(temp->next!=NULL){
		temp=temp->next;
		cnt++;
	}
	return cnt;
}
int insertLast(struct node **head,int no){
	struct node *newNode=(struct node*)malloc(sizeof(struct node));
	newNode->data=no;
	newNode->next=NULL;
	if(*head==NULL){
		*head=newNode;
		newNode->next=NULL;
	}else{
		struct node *temp=*head;
		while(temp->next!=NULL){
			temp=temp->next;
		}
		temp->next=newNode;
	}
	return 0;
}
int insertFirst(struct node **head,int no){
	struct node *newNode=(struct node*)malloc(sizeof(struct node));
	newNode->data=no;
	if(*head==NULL){
		*head=newNode;
		newNode->next=NULL;
	}else{
		newNode->next=*head;
		*head=newNode;
	}
	return 0;
}
int insertAtPos(struct node **head,int no,int pos){
	int cnt=0;
	struct node *temp=*head;
	cnt=count(head);
	if(pos==1){
		insertFirst(head,no);
	}else if(cnt+1==pos){
		insertLast(head,no);
	}else{	
		struct node *newNode=(struct node*)malloc(sizeof(struct node));
		while(pos-1>1){
			temp=temp->next;
			pos--;
		}
		newNode->data=no;
		newNode->next=temp->next;
		temp->next=newNode;
	}
	return 0;
}
void displayLL(struct node **head){
	struct node *temp=*head;
	while(temp->next!=NULL){
		printf("|%d|->",temp->data);
		temp=temp->next;
	}
	printf("|%d|\n",temp->data);
}