Notes

#include<stdio.h>
#include<stdlib.h>
int len;
void create(void);
void append(void);
void addatbegin(void);
void addatafter(void);
int length(void);
void display(void);
void delete(void);
void deletebykey(void);
void reverse(void);
void sum(void);
void merge(void);
struct node
{
int data;
struct node* link;
};
struct node* root=NULL;
struct node* head=NULL;
void main()
{
int ch;
while(1)
{
printf("single linked list operations nn");
printf("1. create a node n");
printf("2. append n");
printf("3. add at begin n");
printf("4. add at after n");
printf("5. length n");
printf("6. display n");
printf("7. delete by locationn");
printf("8. delete by key n");
printf("9. reverse the listn");
printf("10. sum of the elementsn");
printf("11. exitnn");
printf("enter your choice n");
scanf("%d",&ch);
switch(ch)
{
case 1 : create();
break;
case 2 : append();
break;
case 3 : addatbegin();
break;
case 4 : addatafter();
break;
case 5 : len = length();
printf("length : %d n",len);
break;
case 6 : display();
break;
case 7 : delete();
break;
case 8 : deletebykey();
break;
case 9 : reverse();
break;
case 10 : sum();
break;
case 11: exit(1);
default : printf("invalid input: n");
}
}
}

void create()
{
struct node* new;
new=(struct node*)malloc(sizeof(struct node));
printf("enter node data");
scanf("%d",&new->data);
new->link=NULL;
if(root==NULL)
{
root=new;
}
}


void append()
{
struct node* temp;
temp=(struct node*)malloc(sizeof(struct node));
printf("enter node data");
scanf("%d",&temp->data);
temp->link=NULL;
if(root==NULL)
{
root=temp;
}
else
{
struct node* p;
p=root;
while(p->link!=NULL)
{
p=p->link;
}
p->link=temp;
}
}

int length()
{
int count = 0;
struct node* temp;
temp=root;
while(temp!=NULL)
{
count++;
temp=temp->link;
}
len=count;
return len;
}

void display()
{
struct node* temp;
temp=root;
if(temp==NULL)
{
printf("no nodes found, list is empty");
}
else
{
while(temp!=NULL)
{
printf("%d-->",temp->data);
temp=temp->link;
}
printf("nn");
}
}

void addatbegin()
{
struct node* temp;
temp=(struct node*)malloc(sizeof(struct node));
printf("enter node data");
scanf("%d",&temp->data);
temp->link=NULL;
if(root==NULL)
{
root=temp;
}
else
{
temp->link=root; //right side connection
root=temp; //left side connection
}
}

void delete()
{
struct node* temp;
int loc;
printf("enter loaction to delete");
scanf("%d",&loc);
if(loc>length())
{
printf("invalid choice.");
}
else if(loc==1)
{
temp=root;
root=temp->link;
temp->link=NULL;
free(temp);
}
else
{
struct node* p=root, *q;
int i=1;
while(i<loc-1) //pointer p stops at 1 node less than the loacation
{
p=p->link;
i++;
}
q=p->link;
p->link=q->link;
q->link=NULL;
free(q);
}
}

void addatafter()
{
struct node* temp, *p;
int loc, len, i=1;
printf("enter location: n");
scanf("%d",&loc);
len=length();
if(loc>len)
{
printf("invalid input n");
printf("currently list has %d nodes",len);
}
else
{
p=root;
while(i<loc) //pointer p stops at location
{
p=p->link;
i++;
}
}
temp=(struct node*)malloc(sizeof(struct node));
printf("enter node data:");
scanf("%d",&temp->data);
temp->link=NULL;
temp->link=p->link; //right side connection
p->link=temp; //left side connection
}

void deletebykey()
{
struct node* temp, *p, *q;
int key;
temp=root;
if(temp==NULL)
{
printf("empty list");
}
else
{
printf("enter the key value : n");
scanf("%d",&key);
if((temp->data==key) && (temp->link==NULL))
{
p=temp;
root=NULL;
free(p);
}
p=temp;
while((p->link!=NULL) && (p->data!=key))
{
q=p;
p=p->link;
}
if(p->data==key)
{
q->link=p->link;
free(p);
}
else
{
printf("operation not possible n");
}
}
}

void reverse()
{
struct node* temp, *ptr, *curr, *prev;
temp=root;
if(temp==NULL)
{
printf("linked list is emptynn");
return;
}
else
{
curr=temp;
prev=curr->link;
curr->link=NULL;
while(prev->link!=NULL)
{
ptr=prev->link;
prev->link=curr;
curr=prev;
prev=ptr;
}
prev->link=curr;
root=prev;
}
}

void sum()
{
struct node* temp;
int q, sum=0;
temp=root;
if(temp==NULL)
{
printf("linked list is emptynn");
return;
}
else
{
while(temp!=NULL)
{
q=temp->data;
sum=sum+q;
temp=temp->link;
}
printf("the sum of all the elements is %d ",sum);
printf("nn");
}
}