I need some help w/a programming project...

Hey. nonsense. I myself was a college teacher (not in CS thank god) and have to tell you that any Prof. worth a s**t would be delighted to see a student learning stuff on there own and utilizing it to solve problems in a more elegant way. The key is that you have to be able to explain what you did and why you did it. Galathaea has given a good reason why and as for what: Make sure you really understand the solution given. If you are going to tell me that you have a Professor who will frown on learning then I am going to tell you BAH :mad:

Now, the question is are you a good student. Do you want to take the time to learn a little STL so you can solve this problem the C++ way?

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Originally posted by xsyntricity
Well, first of all, I did not select our textbook and have thus been learning all of this the hard way I guess...I am not surprised to see a bad review of the text as it is more geared for a one-time experience with the 'C' programming language and doesn't seem suited for a C.S. major class - even an intro; however, I have no choice but to do this the way my instructor and textbook have taught it...so...I am stuck between a rock and a hard place...again...I am sorry for being such a hassel and now that you know what a hinderance my textbook has been I hope you understand my situation a little better...

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That's OK, since you wouldn't have known before-hand what you should have expected.

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Here is a quote from my text:

"Most of C is a subset of C++ , and so most C programs are also C++ programs."

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This is not entirely true. There are gobs of 'C' programs that cannot compile under C++. Here is one such example:

Code:

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int main()
{
    int class = 1;
    int template  = 2;
}

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I hope you see why this would compile perfectly good 'C' code, but would make the C++ compiler throw up errors all over the place. What this should say is that "you can get a 'C' program to compile under a C++ compiler" and not that "most C is a subset of C++"

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This is why I was under the assumption I was programming in C++

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The problem is that many concepts that a C programmer would learn are not the same concepts that a C++ programmer should learn. Basically C and C++ are two separate languages, where each has ways of doing things properly. When you get to the chapter on handling strings, how does the author of your book explain how to do this? (I shudder to see what is in there concerning string handling)

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is there any way to get this done without using vectors or '*'s?

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The '*' is a pointer. When you deal with arrays, pointers are brought into play, whether you officially learned them or not. This is another reason why vector<> is easier -- you wouldn't have to know squat about pointers. But since you are using arrays, pointer knowledge is part of the deal. It is harder to "dumb-down" the code enough to not use pointers. So your best bet is to understand them now -- you're using arrays anyway.

Regards,

Paul McKenzie

Did my post not make sense to you either? I tried to keep it simple like your class. I was a TA for a while so I can relate to "having to use the basics" I thought I kept it pretty simple :confused:

let me know if you need me to clarify.

My ears and eyes are wide open...I have 'till tomorrow morning...i am using the g++ compiler(not sure what version) on a standard linux box...if you can explain how to make this work using STL i would be delighted to find out as I am a C.S. major and hope to be doing this stuff for a living some day. However, if I don't have a good explaination for why I did what I did my prof. won't be too impressed...so if you guys really feel like teaching a little beginner C++ I will stay here at my computer in this forum...I have all night...

;-)

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Originally posted by souldog
Hey. nonsense. I myself was a college teacher and have to tell you that any Prof. worth a s**t would be delighted to see a student learning stuff on there own and utilizing it to solve problems in a more elegant way.

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Hear, hear. I also taught programming in college, and nothing would be more delightful than seeing a beginning student learn on their own.

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The key is that you have to be able to explain what you did and why you did it.

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Exactly. If you can explain what you did, that is all that is necessary. Believe it or not, this is a trick used on some "do my homework for me" posters (not xsyntricity, you know, the ones that show no work whatsoever, but wants one of us to come up with the answer). What would happen is that the most advanced programming concepts are used to solve the problem. The trick is that the student hands in the assignment, and the professor sees that there is no way a beginning student could have come up with the code. Then the student has to sit (or stand there) and explain what his/her code is doing.

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Galathaea has given a good reason why and as for what: Make sure you really understand the solution given. If you are going to tell me that you have a Professor who will frown on learning then I am going to tell you BAH :mad:

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Yes. As long as you can explain yourself, no professor should object to you learning on your own.

Regards,

Paul McKenzie

Eli...your post didn't make a whole lot of sense to me...sorry ;-)...as for pointers...i kind of thought that's what the * was but I didn't want to embarass myself more than I already have by guessing...also...if they are a part of arrays and would be the easiest way to do this i would love an explanation so that my prof. won't be angry i made use of them without us going over them...as for strings in my text...we haven't got that far but the subsections include an array type for strings, c-string variables, intro to the standard class "string", string processing with the class "string" and then it goes on to vectors...i see what you mean by this being a sh*tty text though...check this out...chapter 10 is arrays(what we are doing now), chapter 11 are strings and vectors, and chapter 12 are pointers and dynamic arrays...seems like it skips around a lot...also...if you could see the dependency chart you would probably throw up...

I guess the 1st order of business is what have you learned? You could create and array of structures where you'd have the value and a count ... That would give you all you'd need ... Then you can do your mathematical operations from there ...

also...i can show you my whole program if you want to...this isn't a "do my homework" thing as I already have a running program...just that one function doesn't do everything it needs to...i have included a typescript attachment of the code and the program running...

int* <-- you are correct, that is a pointer.

Check this out:

Code:

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void CreateArray(int* pvar, int size)
{
pvar = new int[size];
}
void main()
{
int* IWantAnArray;
CreateArray(IWantAnArray, 10);
*IWantAnArray[0] = 1; // legal
}

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ok so I passed in a pointer to an integer to a function. What the function did, then, was create a new array at the pointer address of pvar. Now, a pointer is pointing to an address. To get what's at that address, you use the * operator.

Code:

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int* x;
int y = 4;
x = &y; // now pointing to the address of y
cout << *x << endl; // use * to get the value at the address (4)

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So, since what's at my address in IWantAnArray is a newly created array, you use * to get at the value, and then you use standard array subscripting to get at the actual array, so [0], through [9] in this case.

Basically, I created an array on the fly of the exact size that you need for your code. You would pass in a variable of type int* just like I did here.

It's a shame that you can't use vector, cuz it would have been sooooo much easier :) I haven't used the method that I just explained in ages, so I hope it makes sense (and I hope I didn't F' it up :))

when you say "pointing" to the address, do you mean the memory address?

I would love to help! First, a little bit about vector. As you may have noticed, arrays are very difficult to work with and can be the source of errors since you always need to know how big it is, and that doesn't come packaged with the array. So you are always stuck passing around two values, which is not good c++ style because the whole goal of c++ is to encapsulate related information in things called objects and not have to reveal all the difficult pieces to clients (in simple terms, clients are functions that use the related information). Also, you probably have realized that arrays can never change size, and that is often frustrating and the source of errors.

Enter vector to the rescue! A vector is an array of data that can grow and keeps track of the size so you don't have to. To use it, you must first

Code:

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#include <vector>

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in the file that wants to use it.
Then you just make a vector instance like this

Code:

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std::vector<int> myIntegerVector;

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Where I have placed int, you put whatever type you want the array to be. It could be float, or some structure you have defined (structures and classes are types that you can define yourself -- you will find out about them in good time), or pointers, or all sorts of things. The strange <> brackets you will learn eventually have to do with templates, but again it is not something you have to worry about until you get there. You can use the vector without having to know anything about structures, classes, or templates. And the strange looking std:: before the name vector tells you the "namespace" where vector lives. I see you have

Code:

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using namespace std;

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in your code, so maybe you have learned something about namespaces. If not, you just need to know that the "using" keyword lets you use all of things living in the namespace that you have included without needing to type the std:: part. So you can actually just use

Code:

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vector<int> myIntegerVector;

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if you have the "using" line before the place you make your vector.

So my first suggestion is to get rid of your arrays (and the annoying size you have to keep passing around with it) and replace them with vectors. They are much safer and easier to use in the long run. And this would be a good time to see if you can get some information on the internet about how to use vector's, but don't worry, we can help you out with that as well. The first things you will want to be able to do is to set its size and be able to put some things into it. Here you will learn about using the "." in c++, which is the first step in using many of the wonderful things already lying around in the c++ language...

yeah, that's all a pointer does.

Consider this analogy:
int x;
consider int to be a house. When you do int x; you create a new house on a street somewhere.
int* y = &x; consider y to be the mailbox for the house. It's not the actual house, but it relates to the house -- it is the address of the house. If x didn't exist, then y would be useless in this example.

Anyway, I think your teacher's a little unrealistic. If you want to make your life easier, here's what I'd do:
pass in another array, the same size as your int array[].

Remove the "= new int[whatever]" code and just assume you have a second array the same size as your main array. Fill in the spots of the second array like you did the first array, and then return the integer just like you did before. Most of your second array will be unused, but oh well, if it's easier for you go that route.

I'd sit back and read all the posts (the ones that didn't contain the unnecessary arguements of C vs C++) and try them for a minute and see if anything clicks... try to do something on your own then come back to the forum if nothing is clicking.

good luck!

Quote:

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Originally posted by xsyntricity
also...i can show you my whole program if you want to...this isn't a "do my homework" thing as I already have a running program...just that one function doesn't do everything it needs to...i have included a typescript attachment of the code and the program running...

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Well, here is Caronte's code rewritten using vector:

Code:

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#include <vector>
#include <iostream>

using namespace std;

void mode(const vector<int>& array, vector<int>& data)
{
    int count = 0;
    int max = 0;
    int nSize = array.size();
    data.resize( nSize );

    int count2 = 0;

    for(int i = 0; i < nSize; i++)
    {
        count = 0;
        for(int j = i; j < nSize; j++)
        {
            if(array[i] == array[j])
            {
                count++;
            }
        }
        if(count > max)
        {
            max = count;
            count2 = 0;
            data[count2] = array[i];
        }
        else if(count == max)
        {
            count2++;
            data[count2] = array[i];
        }
    }

    count2++;
    data.resize( count2 );
}

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Note the absence of pointers in the mode function. There are also no hard-coded values that determine the maximum number of items to deal with. So you can have 1 item or 1,000,000 items, the mode() function will still work with no modification. The second parameter is another vector that will store the output -- this way the original vector that was passed in (the first argument) doesn't get overwritten.

So you can go with this if you want -- I didn't document it, because that is your job if you have to explain this to your professor.

Regards,

Paul McKenzie

If you go to this great page you will find Gabriel Fleseriu's beautiful introduction into using vectors in c++. It will be a great start for you!

well guys...i finally got it...and best of all...i didn't use any of you guys' code...just sat down and did it the hard way...so here it is...my mode function(with arrays instead of vectors and no pointers...i know, i know)

Code:

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void mode(int array[], int SIZE_OF_ARRAY, int mode_array[]
        ,int& mode_array_size)
{

        using namespace std;

        int counter;
        int mode_value;
        int max = 0;
        int mode_index = 0;
        int frequency_array[SIZE_OF_ARRAY];

        for (int i = 0; i < SIZE_OF_ARRAY; i++)
        {
                counter = 0;

                for (int j = 0; j < SIZE_OF_ARRAY; j++)
                {
                        if (array[i] == array[j])
                        {
                                counter++;
                        }
                }

                frequency_array[i] = counter;

                if (counter > max)
                {
                        max = counter;
                }
        }

        mode_value = array[0];

        mode_array_size = 0;

        if (frequency_array[0] == max)
        {
                mode_array[mode_index++] = array[0];
                mode_array_size++;
        }

        for (int i = 1; i < SIZE_OF_ARRAY; i++)
        {
                if ((frequency_array[i] == max) && (array[i] != mode_value))
                {
                        mode_array[mode_index++] = array[i];
                        mode_array_size++;
                }


                mode_value = array[i];
        }


}

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