A Simple Illustration of Link List

This is a discussion on A Simple Illustration of Link List within the C Programming forums, part of the General Programming Boards category; Hi, I am not getting Link List at all. Can anybody help me understand it? I have got an example ...

  1. #1
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    Lightbulb A Simple Illustration of Link List

    Hi,


    I am not getting Link List at all. Can anybody help me understand it? I have got an example program which is as follows:

    Code:
    #include <stdio.h>
    
    struct list_el {
       int val;
       struct list_el * next;
    };
    
    typedef struct list_el item;
    
    void main() {
       item * curr, * head;
       int i;
    
       head = NULL;
    
       for(i = 1; i <= 10; i++) {
    
          curr = (item *) malloc( sizeof(item) );
    
          curr->val = i;
    
          curr->next  = head;
          head = curr;
       }
    
       curr = head;
    
       while(curr) {
          printf("%d\n", curr->val);
          curr = curr->next ;
       }
    }

    And here's the output:
    Code:
    10
    9
    8
    7
    6
    5
    4
    3
    2
    1


    Could you explain me the above program statement-wise? And also explain the notation:

    Code:
    typedef struct list_el item;

    Thanks in advance!

  2. #2
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    Here's a good tutorial on linked lists from the FAQ http://faq.cprogramming.com/cgi-bin/...&id=1073086407

  3. #3
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    This is a pretty basic link list example, basically I think of a link list as an object that contains two things 1. A data entry 2.Pointer(s) to another object of the same type. This pointer(s) represents the next element in a list.

    If you use an array for example the element A[1] would have a pointer to A[2](intuitively speaking)

    the line:

    typedef struct list_el item;

    basically allows reference to the data type 'struct list_el' to be 'item', therefore you can just use item instead having to write struct list_el, it is not a necessary declaration for the program to work.

    Code:
    #include <stdio.h>
    
    struct list_el {  //This is basically the declaration of the type of element to be used in thel linklist
       int val;  //some data value
       struct list_el * next; //pointer to next element in link list
    };
    
    typedef struct list_el item; //typedef declaration previously explained
    
    void main() {
       item * curr, * head; //declaring two pointers of type struct
       int i;
    
       head = NULL; 
    
       for(i = 1; i <= 10; i++) {
    
          curr = (item *) malloc( sizeof(item) ); //intuitively your creating an element in the link list, I'm assuming you know what malloc does
    
          curr->val = i; //so you set this new element's value to whatever i is
    
          curr->next  = head; //the pointer to the next element would be set to the previous element created, for the first iteration it would be set to NULL
          head = curr;
       }
    
       curr = head;
       //right now your curr pointer is pointing to the last element created in your link list which is element that has 10 in this case
       while(curr) { //this while loop just traverses the link list starting at curr prints the value and goes to the next element until curr becomes NULL
          printf("%d\n", curr->val);
          curr = curr->next ;
       }
    }
    I'm not sure what your understanding on link lists are so I just wrote everything possible so there might be things you already know. I didn't understand link lists very well the first time I saw them so I know why some people get confused but really they're not that complicated
    Last edited by Albinoswordfish; 12-23-2008 at 05:39 PM.

  4. #4
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    Thumbs up Resolved!

    So, you have done your job quite efficiently and effectively!

    Quote Originally Posted by Albinoswordfish View Post
    This is a pretty basic link list example, basically I think of a link list as an object that contains two things 1. A data entry 2.Pointer(s) to another object of the same type. This pointer(s) represents the next element in a list.

    If you use an array for example the element A[1] would have a pointer to A[2](intuitively speaking)

    the line:

    typedef struct list_el item;

    basically allows reference to the data type 'struct list_el' to be 'item', therefore you can just use item instead having to write struct list_el, it is not a necessary declaration for the program to work.

    Code:
    #include <stdio.h>
    
    struct list_el {  //This is basically the declaration of the type of element to be used in thel linklist
       int val;  //some data value
       struct list_el * next; //pointer to next element in link list
    };
    
    typedef struct list_el item; //typedef declaration previously explained
    
    void main() {
       item * curr, * head; //declaring two pointers of type struct
       int i;
    
       head = NULL; 
    
       for(i = 1; i <= 10; i++) {
    
          curr = (item *) malloc( sizeof(item) ); //intuitively your creating an element in the link list, I'm assuming you know what malloc does
    
          curr->val = i; //so you set this new element's value to whatever i is
    
          curr->next  = head; //the pointer to the next element would be set to the previous element created, for the first iteration it would be set to NULL
          head = curr;
       }
    
       curr = head;
       //right now your curr pointer is pointing to the last element created in your link list which is element that has 10 in this case
       while(curr) { //this while loop just traverses the link list starting at curr prints the value and goes to the next element until curr becomes NULL
          printf("%d\n", curr->val);
          curr = curr->next ;
       }
    }
    I'm not sure what your understanding on link lists are so I just wrote everything possible so there might be things you already know. I didn't understand link lists very well the first time I saw them so I know why some people get confused but really they're not that complicated

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