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introduction to linked lists in C

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• Defining a simple linked list structure
  • In Java, you have learned the following to define a Linked list type:

    public class List { int value; // Payload in the List element List next; // Reference variable to a List object !!! // Other non-relevant stuff omitted }

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  • You can define a equivalent Linked list data type in C as follows:

    struct List { int value; // Payload in the List element struct List *next; // Reference variable to a List object !!! }

    Moral of this example:

    You can do same things if different programming languages If you understand the concepts, you can come up with the construct yourself !!!

    I will illustrate how to program linked list in C using what you know in Java !!

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• Creating linked list elements
  • In Java, you have learned the following to create and initialize a Linked list object:

    List p; // Define a reference variable to List objects p = new List( ); // new List( ) creates a List object and return its location // p = new List( ) makes p point to this List object p.value = 4444; // Initialize value (access the value field) p.next = null; // Initialize next

    Comment:

    The new operator in Java will: Reserve (sufficient) memory to store an object return the address of the reserved memory location The address returned by the new operator must be stored in a reference variable so we can access the object later !!!

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  • You can create and initialize a Linked list object in C as follows:

    struct List *p; // Define a reference variable to List objects p = malloc(sizeof(struct List)); // malloc(sizeof(struct List)) creates a List object and return its location // p = malloc(...) makes p point to this List object p->value = 4444; // Initialize value (access the value field) p->next = null; // Initialize next

    Comment: the C library function malloc( ) performs the same task as Java's new operator

    The call malloc(sizeof(struct List)) in C will: Reserve (sufficient) memory to store an struct List object return the address of the reserved memory location The address returned by the malloc( ) function must be stored in a reference variable so we can access the object later !!!

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    We will use these C constructs in a complete program later

    But first, I want to stress an important difference in memory management between Java (that babies you to death) and C....