Chaining Hash Tables (in C)

This is a discussion on Chaining Hash Tables (in C) within the C Programming forums, part of the General Programming Boards category; well, this assignment is an extension of a previous assignment. the first one was a basic singly list list and ...

  1. #16
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    well, this assignment is an extension of a previous assignment. the first one was a basic singly list list and a binary tree. this assignment is a array with chained linked lists and a binary splay tree.

    i'm just unsure how to deal with array of pointers, which is why i'm struggling with it.

  2. #17
    ATH0 quzah's Avatar
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    Code:
    struct foo {
        int bar;
    };
    ...
    struct foo *baz;
    ...
    baz->bar = 10; /* segfault in the making */
    Baz doesn't actually point to an allocated instance of 'struct foo', so you can't try to access 'bar'.


    Quzah.
    Hope is the first step on the road to disappointment.

  3. #18
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    Code:
    struct foo {
        int bar;
    };
    ...
    struct foo *baz;
    ...
    baz->bar = 10; /* segfault in the making */

    hmmm...but that's not what i wrote....i think

    in main.c, i created an instance...of say in your example of foo, i.e foo newFoo, and then i pass it's address into a function, i.e &newFoo. Then i would do newFoo->bar = 10;

  4. #19
    ATH0 quzah's Avatar
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    Quote Originally Posted by vdk_au
    hmmm...but that's not what i wrote....i think
    It's called teaching. I was showing you that you can't access the members of a structure via a pointer, if your pointer doesn't actually point to anything. Now let's look back at my last post, to see if you can make the connection:
    Quote Originally Posted by quzah
    Code:
    for(i=0; i<20; i++)
    {
       ov->array[i]->head = NULL;
       ov->array[i] = NULL;
    }
    "ov" has an array of poitnters. These pointers don't point at any actual instances, so you can't try to access "head". Doing so is why your program crashes.
    There's another problem with this code, that you'd have, if you actually allocated space. It would be a memory leak. But, since you didn't actually allocate anything for your array of pointers to point at, you get a crash.


    Quzah.
    Hope is the first step on the road to disappointment.

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