Question

Assume you have a linked list of integer data.

Q1: Write a method to count the data in the linked list

Q2: Assume that the data in the linked list are sorted. Write a method to search for an element x and calculate its complexity Big‐Oh

Answer 1

Q1 -

The algorithm to count data in a linked list

   CountNode(Node PTR)

   1.   Count = 0
  
   2.   Node temp_ptr = PTR
  
   3.   While temp_ptr is not null
   4.   do
   5.       Count = Count + 1
   6.       temp_ptr = temp_ptr->next
   7.   end
  
   8.   Return Count

C Language equivalent code to implement the method

   int countNodes(Node **head)
   {
       int count = 0;
      
       Node* ptr = *head;
      
       while(ptr)
       {
           count++;
           ptr = ptr->next;
       }
       return count;
   }

Java Language equivalent code to implement the method

public int getCount()
{
Node temp = head;
int count = 0;
while (temp != null)
{
count++;
temp = temp.next;
}
return count;
}

/*******************************************************/

Q2 -

The algorithm to count data in a linked list

   SearchNode(Node PTR, Key)

   1.   Node Result
   2.   Node temp_ptr = PTR
  
   3.   While temp_ptr is not null
   4.   do
   5.       if temp_ptr is key
   6.           Result = temp_ptr
   7.       end if
   8.       temp_ptr = temp_ptr->next
   9.   end loop
  
   10.   Return Count

C Language equivalent code to implement the method

   Node* searchNode(Node **head, int key)
   {
       Node* result = NULL;
       Node* ptr = *head;
      
       while(ptr)
       {
           if(ptr->data == key)
           {
               result = ptr;
           }  
           ptr = ptr->next;
       }
       return result;
   }

Java Language equivalent code to implement the method

   public boolean search(Node head, int x)
{
Node current = head; //Initialize current
while (current != null)
{
if (current.data == x)
return true; //data found
current = current.next;
}
return false; //data not found
}

Since Linked list are unable to caluclate array index by simple performing arithmetic opeartions, hence it is not possible to get an array index for binary search.
Thus the only searching technique that can be used in the case of a linked list is linear search which has a time complexity of O(n).