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Sunday, February 8, 2015
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Operation on Linked List for Data Structure in C Language

9:28 PMSunday, February 8, 2015
Operation on Linked List

Traversing: To visit all the node of a linked list, start from the ROOT and visit first element and from the first element with the help of link field visit the second element, similarly visit all the element till the last node. The last node is recognized by a NULL address in it link field. So, set a pointer variable PTR with ROOT. Process PTRINFO and update PTR by LINK of PTR i.e. PTRPTRLINK. Repeat till the PTR is NULL. The algorithm is as follow:

                    TRAVERSELL(ROOT)
                    [ROOT points to first node’s address of Linked List]
                    PTR<--ROOT
                    Repeat While PTR< >NULL
                      Apply process to PTR-->INFO
                      PTR<--PTR-->LINK
                    [End of while]
                    Exit.
Algorithm to print the contents of a linked list:
                   TRAVERSELL(ROOT)
                   [ROOT points to first node’s address of Linked List]
                   PTR<--ROOT
                   Repeat While PTR< >NULL
                     Write: PTR-->INFO
                     PTR<--PTR-->LINK
                   [End of while]
                   Exit
Recursive Algorithm to traverse a linked list:
                   REC_TRAV (ROOT)
                   [ROOT points to first node’s address of Linked List]
                   IfROOT< >NULL
                      Apply process to PTR-->INFO
                      REC_TRAV(ROOT-->LINK)
                  [End of it]
                  Eixt.

Searching: Searching is nothing but finding a node with the given information for the presence. If it is present search is successful otherwise unsuccessful. Only Linear Search is used to apply the  searching. Searching almost resembles Traversing except that if search is successful traversing is terminated otherwise the linked list is traversed till the end.  

      So, in order to do searching, get the information to be searching and set PTR with ROOT. Compare Information with INFO of PTR, if it is equal ‘search is successful’ and terminate traversing otherwise update PTR with LINK and repeat the process. Continue the operation till the end. The end is recognized by a NULL of PTR.

Algorithm for Searching:
              SEARCHLL (ROOT, IN)
               [IN is Information to search in Linked List]
               PTR<--ROOT
               Repeat While PTR< >NULL AND IN< >PTR-->INFO
                 PTR<--PTR-->LINK
              [End of while]
              If PTR-->INFO=IN Then:
                Write: ‘Search Successful’
              Else:
                Write: ‘Search Unsuccessful’
             [End of If]
             Exit.

Insertion: Adding a new node the linked list is called as Insertion. To insert a node in the linked list, first a NEW node is created. To create a NEW node, memory is requested and the memory is allocated dynamically from free pool. So NEW is made point to AVAIL and AVAIL is updated. To insert a node two situations arise. The list may be a non-ordered or an ordered non-empty linked list.

If the Linked List is non-ordered list, to insert a NEW node, an Information of a node after which the insertion is to be made is given. So that Information is compared with every node of the list for equality, and the location LOC is found. After finding the LOC, LINK of LOC is copied to the LINK of NEW  node and LINK of NEW node and LINK of LOC is copied with NEW i.e.
NEW-->LINK<--LOC-->LINK and LOC-->LINK<--NEW.

If the Linked List is an ordered list, to insert a NEW node, the Information of NEW node is compared with   the Information of every node of the list. When the Information of the node of the list is greater, it is the     location LOC. The NEW  node is to be placed at that LOC.So in this case a TEMP variable is used to store the previous node’s address so that LINK of TEMP gives LOC. Now to insert the node, LINK of  NEW is copied with LOC and LINK of TEMP is copied with NEW. i.e.
 NEW-->LINK<--LOC and TEMP-->LINK<--NEW.

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