singly linked list

This is a discussion on singly linked list within the C Programming forums, part of the General Programming Boards category; I'm currently trying to understand singly linked lists and pointers. Can somebody write more detailed inline comments in the following ...

  1. #1
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    singly linked list

    I'm currently trying to understand singly linked lists and pointers. Can somebody write more detailed inline comments in the following code??

    Thanks in advance.


    Code:
    #include <stdio.h>
    #include <stdlib.h>
    
    struct node {
      int x;
      struct node *next;
    };
    
    int main()
    {
        /* This won't change, or we would lose the list in memory */
        struct node *root;       
        /* This will point to each node as it traverses the list */
        struct node *conductor;  
    
        root = malloc( sizeof(struct node) );  
        root->next = 0;   
        root->x = 12;
        conductor = root; 
        if ( conductor != 0 ) {
            while ( conductor->next != 0)
            {
                conductor = conductor->next;
            }
        }
        /* Creates a node at the end of the list */
        conductor->next = malloc( sizeof(struct node) );  
    
        conductor = conductor->next; 
    
        if ( conductor == 0 )
        {
            printf( "Out of memory" );
            return 0;
        }
        /* initialize the new memory */
        conductor->next = 0;         
        conductor->x = 42;
    
        return 0;
    }

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    I especially wonder why it's necessary to write conductor = root; on line 19.

  3. #3
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by right2001 View Post
    I especially wonder why it's necessary to write conductor = root; on line 19.
    Were you planning to just leave conductor uninitialized, not pointing to anything, and try to use it? Were you planning to start somewhere other than the beginning of the list (since that's what root is, the beginning of the list).

  4. #4
    DESTINY BEN10's Avatar
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    Quote Originally Posted by right2001 View Post
    I especially wonder why it's necessary to write conductor = root; on line 19.
    If conductor=root wasn't there, being a pointer conductor would have pointed to any random location(address), creating several problems. Your rest of the code would have been meaningless. conductor=root will make conductor to point to the beginning of the list or the first node. Also you should use NULL instead of 0 in your code. It will be more meaningful to the context.
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