Explain the logic and code of deletion of a node from a singly linked list.

1. Singly Linked List
A Linear Data Structure
SONI GUPTA
ASSISTANT PROFESSOR (NPIU-TEQIP III )
HBTU KANPUR, UP
TEQIP
-III

2. Deletion operation
TEQIP
-III

3. Deletion of a node
1. Delete first node
2. Delete last node
3. Delete node from given position
TEQIP
-III

4. Delete the first node
 Check if the linked list is empty
 If so return underflow
 Search for the node
 Find its successor and predecessor of the node
 If the end of the list has been reached then return node dose not exist
 Delete the node from the list
 Free the space (deleted node)
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-III

5.  head
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30 40
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6.  ptr head
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30 40
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head=head->next
p->next=NULL

7. void delete_from_first()
{
struct node *ptr;
if(head == NULL)
{
printf("nList is emptyn");
}
else
{
ptr = head;
head = ptr->next;
free(ptr);
printf("nNode deleted from the beginning of the linked list");
}
}
TEQIP
-III

8. Delete the last node
 Check if the linked list is empty
 If so return underflow
 Traverse the list to reach at the predecessor of last node
 Delete the node from the list
 Free the space (deleted node)
TEQIP
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9.  head
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30 40
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10.  Head ptr1 ptr
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11. void delete_from_End(node head)
{
struct node *ptr,*ptr1;
if(head == NULL)
{
printf("nlist is empty");
}
else if(head→ next == NULL)
{
head = NULL;
free(head);
printf("nOnly node of the list deleted ...n");
}
TEQIP
-III

12. else
{
ptr = head;
while(ptr → next != NULL)
{
ptr1 = ptr;
ptr = ptr → next;
}
ptr1 → next = NULL;
free(ptr);
printf("nDeleted Node from the last ...n");
}
}
TEQIP
-III

13. Delete the node from given position
1. Check if the linked list is empty
If so return underflow
2. Search for the node
3. Find its successor and predecessor of the node
4. If the end of the list has been reached then return node dose not exist
5. Delete the node from the list
6. Free the space (deleted node)
TEQIP
-III

14.  head
10 20
30 40
TEQIP
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15.  head
10 20
30 40
TEQIP
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16. void random_delete()
{
struct node *ptr,*ptr1;
int loc,i;
printf("n Enter the position of the node after which you want to perform deletion n");
scanf("%d",&loc);
ptr=head;
for(i=0;i<loc;i++)
{
ptr1 = ptr;
ptr = ptr→ next;
if(ptr == NULL)
{
printf("nGiven position does not exist");
return;
}
}
ptr1 → next = ptr → next;
free(ptr);
printf("nDeleted node %d ",loc+1);
}
TEQIP
-III

17. Search an element in a
given linked list
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18. void search()
{
struct node *ptr;
int item,i=0,flag;
ptr = head;
if(ptr == NULL)
{
printf("nEmpty Listn");
}
else
{
printf("nEnter item which you want to search?n");
scanf("%d",&item);
TEQIP
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19. while (ptr!=NULL)
{
if(ptr → data == item)
{
printf("item found at location %d ",i+1);
flag=0;
}
else
{
flag=1;
}
i++;
ptr = ptr → next;
}
if(flag==1)
{
printf("Item not foundn");
}
}
}
TEQIP
-III