Algorithm to delete a Node from Linked List

Delete_Node_LL(List, Start, value)

Here, List is a Linked list Containing n Nodes.Start is a pointer pointing to the starting node of the List We have to delete a node which contains value as its data. Ptr is an intermediate pointer, which will be used to traverse the List. Prev is a intermediate pointer which will be contains the address of Node which is previous to the node pointing by Ptr

Step 1: [Initializing the pointers Ptr will be pointing the starting node and Prev will be null]

             Ptr = Start, Prev = null

Step 2: [If Node to be deleted is 1st node]

            if Ptr->Data = value then

                  i) Start = Ptr->Next

                  ii) Free(Ptr) [Releasing memory consumed by node to be deleted]

                  iii) Return; 

Step 3:[Since node to be deleted is not starting node so moving Ptr to 2nd node and Prev will be pointing starting node] 

           i)Prev = Ptr

          ii)Ptr = Ptr->Next

Step 4: Repeat Step 4(i) to 4(iv) till Ptr is not null. 

           i) if Ptr->Data = value then

                         a) Prev->Next = Ptr->Next; 

                         b) Free(Ptr); 

                         c) Return;

          ii) Prev = Ptr;

         iii) Ptr = Ptr ->Next

Step 5: [Node was not found raise error or return the control]

            Return;

Click Here for Explanation

Consider a List displayed below

Here       Start=2002
Consider value=54

At starting:

                 
   
Here Ptr = Start=2002.
  
and Ptr->Data = value 
so that according to the step 2 of algorithm

Start = Ptr->Next

Free(Ptr)

      
Similarly, if value=10 then
Ptr->Data = 54 which is not equal to value.
so  Prev = Ptr = 2002
      Ptr = Ptr->Next = 2044

Iteration 1:
Ptr->Data = 45 which is not equals to value
 So Prev = Ptr = 2044
      Ptr = Ptr->Next = 5260

Iteration 2:
Ptr->Data = 10 = Value
 => Prev->Next = Ptr->Next

Free(Ptr)

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