Beginner help

This is a discussion on Beginner help within the C Programming forums, part of the General Programming Boards category; Hi, I have just learned linked lists on C and want to write a program about it. But even this ...

  1. #1
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    Question Beginner help

    Hi,

    I have just learned linked lists on C and want to write a program about it. But even this simple code gives runtime error which I added as attachment.

    Could you help me about it, thanks...
    Attached Files Attached Files

  2. #2
    C++まいる!Cをこわせ! Elysia's Avatar
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    First, I want to point out that malloc is in stdlib.h, but you aren't including it.
    As for the problem, it's because head->next != NULL. You never initialize it to anything, so the program think it's valid.
    Last edited by Elysia; 07-27-2009 at 03:32 PM.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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    The next pointer in head needs to be set to NULL after the first malloc:

    head->next = NULL;

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    Quote Originally Posted by Scarlet7 View Post
    The next pointer in head needs to be set to NULL after the first malloc:

    head->next = NULL;
    Thanks, it works I missed it. But what about the dump value at the end of the list?

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    Registered User Cooloorful's Avatar
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    Why not just write out your values like this?

    Code:
        while(current != NULL){
          if(current->coef != 0)
            printf("%dx%d+",current->coef,current->pow);
          current = current->next;
        }
    wipe on -
    A slap on the hand is better than a slap on the face. A tragic lesson learned far too late in life.
    - wipe off

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    Quote Originally Posted by Cooloorful View Post
    Why not just write out your values like this?

    Code:
        while(current != NULL){
          if(current->coef != 0)
            printf("%dx%d+",current->coef,current->pow);
          current = current->next;
        }
    Maybe but I just try the code to understand

  7. #7
    Registered User Cooloorful's Avatar
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    Code:
        while(current != NULL){
          if(current->coef != 0)
            printf("%dx%d+",current->coef,current->pow);
          current = current->next;
        }
    Ok, the blue sections are your code and won't be explained. The green is mine and I will explain.

    When you are reading in the values you are taking in a final value with a coefficient of 0. You allow it in the list, but you technically only use it to let your program know when to stop reading in new values. Ok, that is fine. Given that fact, why even print something that is basically just a signal to stop reading? So the if statement checks if the coefficient is zero. If the coefficient is zero, the term is skipped.
    wipe on -
    A slap on the hand is better than a slap on the face. A tragic lesson learned far too late in life.
    - wipe off

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    Quote Originally Posted by Cooloorful View Post
    Code:
        while(current != NULL){
          if(current->coef != 0)
            printf("%dx%d+",current->coef,current->pow);
          current = current->next;
        }
    Ok, the blue sections are your code and won't be explained. The green is mine and I will explain.

    When you are reading in the values you are taking in a final value with a coefficient of 0. You allow it in the list, but you technically only use it to let your program know when to stop reading in new values. Ok, that is fine. Given that fact, why even print something that is basically just a signal to stop reading? So the if statement checks if the coefficient is zero. If the coefficient is zero, the term is skipped.
    OK It is the same but have you ever tried to run, when I attempt to exit, a dump value occurs at the end of the list

    THANKS

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