My C++ test is COMING!!...

[Z-D] · 11-25-2006, 05:48 AM

Hey guys. I will be having my C++ open book test on the 5th of December. Luckily its open book. So I need advice from you guys. Any kind advices.

Also I'm very sure that arrays will be included, because the last topic that we learnt was arrays and recently we had a mock C++ test which included arrays. And so far, when it comes to arrays, I'm totally clueless. The reason is because my lecturer is useless in teaching. He's is just as good as, "Here we will be learning arrays. The end. Learn everything yourself." But of course he does try to teach, but nobody in class knows whats going on.

So I've have found a few good web sites on C++ and have a book on C++, but I'm only starting to learn arrays. I have the simple basic for C++, but still, I have no idea on how to use arrays. So while I'm trying to learn it, I taught that may be I could post here and ask for advices and a bit of lessons.

Could anyone give me a simple example of a code using arrays? How about, arranging numbers from smallest to biggest?

I will scan my mock test and post it here later, so that you guys have a better Idea of the test. And since its an open book test, we are allowed to have notes during the test, whether on paper or even on the internet.

So would it be okay if I log on this site during the test? But no cheating of course... May be to help me out a bit?

**laserlight** · 11-25-2006, 06:16 AM

Quote:

How about, arranging numbers from smallest to biggest?

You could search the Web concerning sorting algorithms. Sorting Algorithms

therabidwombat · 11-25-2006, 01:31 PM

I think that if he can't understand arrays at this point, then sorting algorithms may be a little beyond his current abilities.

For arrays, it's really quite simple if you understand variables. All that an array is is a variable. so what makes an array different, you ask? Well, for one thing, arrays are more than one variable.

Here's the example that I've seen used numerous times when describing arrays: Suppose that you have six numbers. Each one is the id of an object. So we'd have

Code:

int id1, id2, id3, id4, id5, id6;
id1 = 0;
id2 = 1;
id3 = 5;
id4 = 7;
id5 = 2;
id6 = 4;

Now, as you can see, all of these numbers are related, yet they're all seperate variables. But if you use an array, you can do this:

Code:

int id[6];
id[0] = 0;
id[1] = 1;
id[2] = 5;
id[3] = 7;
id[4] = 2;
id[5] = 4;

the [n] area of each array is called it's 'indice'. Note that arrays start at an indice zero; as such, when you declare an array of length 6 (by going int id[6]), you end up with an array with indices from zero to five.

What's the point of this? At first, there doesn't seem to be much of any. However, there are several uses, one of the most common uses is that arrays and for loops are built for each other. Instead of having to do:

Code:

cout << id1 << "\n";
cout << id2 << "\n";
coud << id3 << "\n"
...

you could do

Code:

for(int i = 0; i < 6; i++)
cout << id[i] << "\n";

dwks · 11-25-2006, 02:18 PM

There's a tutorial on arrays, I don't know if you've seen it: http://www.cprogramming.com/tutorial/lesson8.html

Basically, an array is a convenient name for many different variables as the previous poster has indicated.

[Z-D] · 11-25-2006, 04:34 PM

Thanks alot guys,.... I've been reading on this a lot for the past don't know how many hours.
I mannage to understand a bit.

laserlight, I went through that site but It was kind of hard to understand completely. About the Bubble sort code,

Code:

void bubbleSort(int numbers[], int array_size)
{
  int i, j, temp;

  for (i = (array_size - 1); i >= 0; i--)
  {
    for (j = 1; j <= i; j++)
    {
      if (numbers[j-1] > numbers[j])
      {
        temp = numbers[j-1];
        numbers[j-1] = numbers[j];
        numbers[j] = temp;
      }
    }
  }
}

How will the output turn out?

therabidwombat: Thanks a lot! I mannaged to understand the basic already.

But what I noticed in the lecture slides provided by the lecturer is that all the values in the arrays are all fixed. For example

Code:

const int responseSize = 99;
	response[ responseSize ] = 
		{ 6, 7, 8, 9, 8, 7, 8, 9, 8, 9,
		7, 8, 9, 5, 9, 8, 7, 8, 7, 8,
		7, 8, 9, 8, 9, 8, 9, 7, 8, 9,
		7, 8, 9, 8, 9, 8, 9, 7, 5, 3,
		5, 6, 7, 2, 5, 3, 9, 4, 6, 4,
		7, 8, 9, 6, 8, 7, 8, 9, 7, 8,
		7, 4, 4, 2, 5, 3, 8, 7, 5, 6,
		4, 5, 6, 1, 6, 5, 7, 8, 7 };

I understand that all these numbers becomes the values stored in the arrays, but how do we input our own values to be stored? I can't seem to get any info on that.

There is more which I don't understand. Well actually the code starts with this:

Code:

#include <iostream.h>
#include<iomanip.h>


void mean(const int[], int);
void median(int[], int)
void mode(int[], int[], int)
void bubbleSort(const int[], int);

int main()
{

	const int responseSize = 99;
		response[ responseSize ] = 	
			{ 6, 7, 8, 9, 8, 7, 8, 9, 8, 9,
			7, 8, 9, 5, 9, 8, 7, 8, 7, 8,
			7, 8, 9, 8, 9, 8, 9, 7, 8, 9,
			7, 8, 9, 8, 9, 8, 9, 7, 5, 3,
			5, 6, 7, 2, 5, 3, 9, 4, 6, 4,
			7, 8, 9, 6, 8, 7, 8, 9, 7, 8,
			7, 4, 4, 2, 5, 3, 8, 7, 5, 6,
			4, 5, 6, 1, 6, 5, 7, 8, 7 };

	mean( response, responseSize );
	median( response, responseSize );
	mode( frequency, response, responseSize );

	return 0;
}

...
...

then it goes on to defining mean then median...
here's the code for defining median:

Code:

void median( int answer[], int size )
{
	cout << "\n********\n Median\n********\n"
		<< "The unsorted array of responses is";
	printArray( answer, size );
	bubbleSort( answer, size );
	cout << "\n\nThe sorted array is";
	printArray( answer, size );
	cout << "\n\nThe median is element " << size / 2
		<< " of\nthe sorted " << size 
		<< " element array.\nFor this run the median is "
		<< answer[ size / 2 ] << "\n\n";

and the output for the median is:

Code:

********
 Median
********
The unsorted array of responses is
 6 7 8 9 8 7 8 9 8 9 7 8 9 5 9 8 7 8 7 8
 6 7 8 9 3 9 8 7 8 7 7 8 9 8 9 8 9 7 8 9
 6 7 8 7 8 7 9 8 9 2 7 8 9 8 9 8 9 7 5 3
 5 6 7 2 5 3 9 4 6 4 7 8 9 6 8 7 8 9 7 8
 7 4 4 2 5 3 8 7 5 6 4 5 6 1 6 5 7 8 7
 
The sorted array is
 1 2 2 2 3 3 3 3 4 4 4 4 4 5 5 5 5 5 5 5
 5 6 6 6 6 6 6 6 6 6 7 7 7 7 7 7 7 7 7 7
 7 7 7 7 7 7 7 7 7 7 7 7 7 8 8 8 8 8 8 8
 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8
 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9
 
The median is element 49 of
the sorted 99 element array.
For this run the median is 7

What I don't understand is how did they values get all sorted up. I noticed that the sorting was done by this part of the code:

Code:

printArray( answer, size );

But how? How was answer and size defined?

and, to dwks: Yeah I did check that out. The explanation seems to be too general and less technical. Thanks anyway.

[Z-D] · 11-25-2006, 04:48 PM

Wait, wait....

May be I got it. Is this how you input the values?

Code:

int main();
{
	int grades[10]

	for (int i = 0; i < 4; 4; i++)
	{
		cout << "Enter 10 grades: ";
		cin >> grades[i];
	}

Did I get it right?

Desolation · 11-25-2006, 04:56 PM

Your for() loop is wrong, it should read for(int i = 0; i < 10; i++). There also lacks a closing brace and you have an extra semi-colon after int main(). Oh, and you lack a semi-colon after int grades[10];

[Z-D] · 11-25-2006, 05:59 PM

Oh yeah... mistakes. Thanks. So it should be:

Code:

int main();
{
	int grades[10];

	for(int i = 0; i < 10; i++);
	{
		cout << "Enter 10 grades: ";
		cin >> grades[i];
	}
...
...
...

	return 0;
}

So, about the median thingy... How did they get sorted? I don't get it...

swgh · 11-25-2006, 06:30 PM

>int main();

Still got a semi-colon here

Desolation · 11-25-2006, 08:55 PM

Quote:

Originally Posted by [Z-D]

What I don't understand is how did they values get all sorted up. I noticed that the sorting was done by this part of the code:

Code:

printArray( answer, size );

But how? How was answer and size defined?

Wrong. It is done by the bubbleSort() function. The median() function simply shouldn't be there... really.. It hides the whole purpose of the bubble sort. It first displays the unsorted array, then calls bubbleSort() which sorts the array and then displays the now-sorted array. This is your typical before-after comparison.

If you are wondering how the bubble sort works well you can take a sheet of paper and a pencil and work by hand what it's doing. You'll learn a lot more. I find it's a twisted version of the bubble sort, though. The way I know it is much simpler. Whatever.

Code:

void bubbleSort(int numbers[], int array_size)
{
  int i, j, temp;

  for (i = (array_size - 1); i >= 0; i--)
  {
    for (j = 1; j <= i; j++)
    {
      if (numbers[j-1] > numbers[j])
      {
        temp = numbers[j-1];
        numbers[j-1] = numbers[j];
        numbers[j] = temp;
      }
    }
  }
}

This basically means this:

Code:

for ( all entries in the array, going backwards )
{
  for ( all the entries from 1 to i )
  {
    if( the entry at the location j - 1 ( 0, 1 , 2 ... i ) is greater than the entry next to it)
    {
      switch the values
    }
  }
}

Basically, what it does is simple. You start by going through all the numbers from the beginning to end and switch the entries so that the biggest number becomes last in the array. Then, 'i' decreases so you don't have to check the last number because you know for sure that it is the biggest in the array. The reason why 'j' is set to 1 in the second for() loop is because when you have done n - 1 iterations, the last number not sorted is surely the smallest in the array, thus you don't need to proceed further. However, the code has something weird. The first for() loops until i is equal to 0 and then it finishes... and the second says "execute if j is <= i" ... however, j is set to 1 in the first place. Therefore, when i will equal 0, the first for() loop will be executed, but the second will not. This is no biggie. No bug, no leak, no blue-screen-of-death. Just useless. It could be fixed by simply changing "i >= 0" to "i >= 1".

Edit: Just in case you're visual:

This is the list to sort:

4 7 1 5 3

Here's what happens

Code:

  j     i
4 7 1 5 3

You always have to j - 1 to j and switch if j - 1 is greater than j

    j   i
4 7 1 5 3

      j i
4 1 7 5 3

        ji (both on 3)
4 1 5 7 3

  j   i
4 1 5 3 7

    j i
1 4 5 3 7

      ji (both on 3)
1 4 5 3 7

  j i
1 4 3 5 7

    ji (both on 3)
1 4 3 5 7

1 3 4 5 7

Hope this helps you.

[Z-D] · 11-26-2006, 02:04 AM

Quote:

Originally Posted by swgh

>int main();

Oh darn.... Yeah. Got that, thanks.

Quote:

Originally Posted by Desolation

Wrong. It is done by the bubbleSort() function. The median() function simply shouldn't be there... really.. It hides the whole purpose of the bubble sort. It first displays the unsorted array, then calls bubbleSort() which sorts the array and then displays the now-sorted array. This is your typical before-after comparison.

Ummm... What's wrong? The code given is wrong?... Those are from my lecturer. I guess he's worst than I taught.

Quote:

Originally Posted by Desolations

However, the code has something weird. The first for() loops until i is equal to 0 and then it finishes... and the second says "execute if j is <= i" ... however, j is set to 1 in the first place. Therefore, when i will equal 0, the first for() loop will be executed, but the second will not. This is no biggie. No bug, no leak, no blue-screen-of-death. Just useless. It could be fixed by simply changing "i >= 0" to "i >= 1".

Thanks... If it is fixed to...

Code:

i>=1

...does that mean that the process will stop at i = 0? What if I change "j = 1" to "j = 0" instead? Will this also work?

So if I do this,

Code:

	for (i = (array_size -1); i >=0; i--)
	{
		for (j = 0; j <=i; i++)

Instead of stopping at i = 1, the sorting will stop when i = 0... Am I right?

Quote:

Originally Posted by Desolation

Edit: Just in case you're visual:

This is the list to sort:

4 7 1 5 3

Here's what happens

Code:

  j     i
4 7 1 5 3

You always have to j - 1 to j and switch if j - 1 is greater than j

    j   i
4 7 1 5 3

      j i
4 1 7 5 3

        ji (both on 3)
4 1 5 7 3

  j   i
4 1 5 3 7

    j i
1 4 5 3 7

      ji (both on 3)
1 4 5 3 7

  j i
1 4 3 5 7

    ji (both on 3)
1 4 3 5 7

1 3 4 5 7

Hope this helps you.

Ohhh hell,.... Yeah! That helped a lot! Thanks a lot.

So will this work?

Code:

int main()
{
	int numbers[10];

	for (int i = 0; i < 10; i++);
	{
		cout << "Enter 10 grades: ";
		cin >> numbers[i];
		cout << "Your sorted grades are: ";

	bubbleSort(int numbers[], int array_size);
	}

	return 0;
}

void bubbleSort{int numbers[], int array_size)
{
	int i, j, grades;

	for (i = (array_size -1); i >=0; i--)
	{
		for (j = 0; j <=i; i++)
		{
			if (numbers[j-1] > numbers[j])
			{
				grades = numbers[j-i]
				numbers[j-1] = numbers [j];
				number[j] = grades;
			}
		}
	}

}

Sorry if this code bothers you with the amound of mistakes, if there is. I'm still kind of blur you know!...

This is the output that I'm trying acheive:

Code:

Out put:
Enter 10 grades: 15, 24, 12, 99, 58, 47, 26, 45, 87, 55 <---- then we enter grades here
Your sotrt grades are: 12, 15, 24, 26, 45, 47, 55, 58, 87, 99   <----- this is the sorted one

But there's something I need to know. I want these values to be equals to more than 0 and equals to less than 100.

Desolation · 11-26-2006, 09:45 AM

1. You were wrong when you said the sorting was done by printArray().
2. No, changing j = 1 to j = 0 will crash your program. Try to find why, as an exercise.
3. Not changing i >= 0 will simply leave you with an useless for() loop executed. You have to change it to i >= 1 to get rid of it because then when i equals 1, the second for() loop will get executed as well (since it is executed for j <= i).

[Z-D] · 11-27-2006, 08:52 AM

Okay then. But how do we display the arrange set of numbers in the output?

And supposing I want the programme to be able to input 10 numbers(or grades) then arrange and output the numbers. How do set it so that "i" must be between 0 and 100? Meaning equals or more than 0 and equals or less than 100.

Was my code in my previous code correct? I couldn't seem to get it right.

Okay so this is from the lecturers notes...

Code:

#include <iostream.h>
#include<iomanip.h>


void mean(const int[], int);
void median(int[], int)
void mode(int[], int[], int)
void bubbleSort(const int[], int);

int main()
{

	const int responseSize = 99;
		response[ responseSize ] = 	
			{ 6, 7, 8, 9, 8, 7, 8, 9, 8, 9,
			7, 8, 9, 5, 9, 8, 7, 8, 7, 8,
			7, 8, 9, 8, 9, 8, 9, 7, 8, 9,
			7, 8, 9, 8, 9, 8, 9, 7, 5, 3,
			5, 6, 7, 2, 5, 3, 9, 4, 6, 4,
			7, 8, 9, 6, 8, 7, 8, 9, 7, 8,
			7, 4, 4, 2, 5, 3, 8, 7, 5, 6,
			4, 5, 6, 1, 6, 5, 7, 8, 7 };

	mean( response, responseSize );
	median( response, responseSize );
	mode( frequency, response, responseSize );

	return 0;
}

void mean( const int answer[], int arraySize )
{
	int total = 0;

	cout << "********\n  Mean\n********\n";

	for ( int j = 0; j < arraySize; j++ )
		total += answer[ j ];

	cout << "The mean is the average value of the data\n"
		<< "items. The mean is equal to the total of\n"
		<< "all the data items divided by the number\n"
		<< "of data items (" << arraySize 
		<< "). The mean value for\nthis run is: " 
		<< total << " / " << arraySize << " = "
		<< setiosflags( ios::fixed | ios::showpoint )
		<< setprecision( 4 )
		<< static_cast< double >( total ) / arraySize << "\n\n";
}


void median( int answer[], int size )
{
	cout << "\n********\n Median\n********\n"
		<< "The unsorted array of responses is";
	printArray( answer, size );
	bubbleSort( answer, size );
	cout << "\n\nThe sorted array is";
	printArray( answer, size );
	cout << "\n\nThe median is element " << size / 2
		<< " of\nthe sorted " << size 
		<< " element array.\nFor this run the median is "
		<< answer[ size / 2 ] << "\n\n";
}


	void mode( int freq[], int answer[], int size )
{
	cout << "\n********\n  Mode\n********\n";

	int rating, largest = 0, modeValue = 0;

	for ( rating = 1; rating <= 9; rating++ )
		freq[ rating ] = 0;

	for ( int j = 0; j < size; j++ )
		++freq[ answer[ j ] ];

	cout << "Response"<< setw( 11 ) << "Frequency"
		<< setw( 19 ) << "Histogram\n\n" << setw( 55 )
		<< "1    1    2    2\n" << setw( 56 )
		<< "5    0    5    0    5\n\n";

	for ( rating = 1; rating <= 9; rating++ )

	cout << setw( 8 ) << rating << setw( 11 )
		<< freq[ rating ] << "          ";
		if ( freq[ rating ] > largest )
		{
			largest = freq[ rating ];
			modeValue = rating;
		}

		for ( int h = 1; h <= freq[ rating ]; h++ )
			cout << '*';
			cout << '\n';
	}
	cout << "The mode is the most frequent value.\n"
		<< "For this run the mode is " << modeValue
		<< " which occurred " << largest << " times." << endl;
}


void bubbleSort( int a[], int size )
{
	int hold;
	for ( int pass = 1; pass < size; pass++ )

		for ( int j = 0; j < size - 1; j++ )

			if ( a[ j ] > a[ j + 1 ] )
			{
				hold = a[ j ];
				a[ j ] = a[ j + 1 ];

				a[ j + 1 ] = hold;
			}
}


void printArray( const int a[], int size )
{
	for ( int j = 0; j < size; j++ )
	{
		if ( j % 20 == 0 )
			cout << endl;
			cout << setw( 2 ) << a[ j ];
	}
}

And the output is suppose to be:

Code:

//Output:
********
  Mean
********
The mean is the average value of the data
items. The mean is equal to the total of
all the data items divided by the number
of data items (99). The mean value for
this run is: 681 / 99 = 6.8788
 
 
********
 Median
********
The unsorted array of responses is
 6 7 8 9 8 7 8 9 8 9 7 8 9 5 9 8 7 8 7 8
 6 7 8 9 3 9 8 7 8 7 7 8 9 8 9 8 9 7 8 9
 6 7 8 7 8 7 9 8 9 2 7 8 9 8 9 8 9 7 5 3
 5 6 7 2 5 3 9 4 6 4 7 8 9 6 8 7 8 9 7 8
 7 4 4 2 5 3 8 7 5 6 4 5 6 1 6 5 7 8 7

The sorted array is
 1 2 2 2 3 3 3 3 4 4 4 4 4 5 5 5 5 5 5 5
 5 6 6 6 6 6 6 6 6 6 7 7 7 7 7 7 7 7 7 7
 7 7 7 7 7 7 7 7 7 7 7 7 7 8 8 8 8 8 8 8
 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8
 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9
 
The median is element 49 of
the sorted 99 element array.
For this run the median is 7
********
  Mode
********
Response  Frequency        Histogram
 
                                      1    1    2    2
                                 5    0    5    0    5
 
       1          1          *
       2          3          ***
       3          4          ****
       4          5          *****
       5          8          ********
       6          9          *********
       7         23          ***********************
       8         27          ***************************
       9         19          *******************
The mode is the most frequent value.
For this run the mode is 8 which occurred 27 times.

...and when I tested it, it didn't work.
What are the mistakes in this code? Also, I'm tyring to understand it, but there is some part which I have difficulty understanding. What I'm interested in is how the the numbers got sorted. Also I don't understand almost the whole part of defining mean.

I'm trying to do something like this, where the programme can sort the numbers, but the numbers are input-ed instead of given.

This is what I came up with so far. I'm just trying to sort the inputed numbers here. Would this work.

Code:

#include <iostream.h>
#include<iomanip.h>

void bubbleSort(int numbers[], int array_size);			//initialise arrays

int main(void)							//call fucntion
{
	int numbers[10];

	for (int i = 1; i < 10; i++);
	{
		cout << "Enter 10 grades: ";
		cin >> numbers[i];
		cout << "Your sorted grades are: ";

	bubbleSort(int numbers[], int array_size);
	}

	return 0;
}

void bubbleSort(int numbers[], int array_size)			//defining bubleSort
{
	int i, j, grades;

	for (i = (array_size -1); i >=1; i--)
	{
		for (j = 1; j <=i; i++)	
		{
			if (numbers[j-1] > numbers[j])
			{
				grades = numbers[j-i]
				numbers[j-1] = numbers [j];
				number[j] = grades;
			}
		}
	}

}

elad · 11-27-2006, 10:36 AM

>>What are the mistakes in this code?

After a quick look through, there should be a { between the following two lines:

Code:

for ( rating = 1; rating <= 9; rating++ )

	cout << setw( 8 ) << rating << setw( 11 )

I'd prefer this:

Code:

for ( int h = 1; h <= freq[ rating ]; h++ )
	cout << '*';
	cout << '\n';

look like this:

Code:

for ( int h = 1; h <= freq[ rating ]; h++ )
      cout << '*';
cout << '\n';

to be more clear in the intention, but it's not wrong as posted and the indentation may be a problem with the board and not the author.

>>Would this work

Run it and find out. The big problem I see is you are sorting with every input, which is time intensive. Moving these two lines out of the loop may be better.

cout << "Your sorted grades are: ";
bubbleSort(int numbers[], int array_size);

[Z-D] · 11-27-2006, 11:00 AM

Quote:

Originally Posted by elad

>>Would this work

Run it and find out.

Well,.... he, he,..... the thing is that... ummmm.... I don't have a compiler at home. I need to test it in my Com Lab.

I better buy one.

Quote:

Originally Posted by elad

The big problem I see is you are sorting with every input, which is time intensive.

What do you mean by sorting ever input?... You mean this part?

Code:

void bubbleSort(int numbers[], int array_size)			//defining bubleSort
{
	int i, j, grades;

	for (i = (array_size -1); i >=1; i--)
	{
		for (j = 1; j <=i; i++)	
		{
			if (numbers[j-1] > numbers[j])
			{
				grades = numbers[j-i]
				numbers[j-1] = numbers [j];
				number[j] = grades;
			}
		}
	}

}

Quote:

Originally Posted by elad

Moving these two lines out of the loop may be better.

cout << "Your sorted grades are: ";
bubbleSort(int numbers[], int array_size);

You mean like this?

Code:

int main(void)							//call fucntion
{
	int numbers[10], i, j;



	for (int i = 1; i < 10; i++);
	{
		cout << "Enter 10 grades: ";
		cin >> numbers[i];
	}
		cout << "Your sorted grades are: ";

	bubbleSort(int numbers[], int array_size);

	return 0;
}

11-25-2006, 05:48 AM	#1
[Z-D] Registered User Join Date: Oct 2006 Posts: 37	My C++ test is COMING!!... Hey guys. I will be having my C++ open book test on the 5th of December. Luckily its open book. So I need advice from you guys. Any kind advices. Also I'm very sure that arrays will be included, because the last topic that we learnt was arrays and recently we had a mock C++ test which included arrays. And so far, when it comes to arrays, I'm totally clueless. The reason is because my lecturer is useless in teaching. He's is just as good as, "Here we will be learning arrays. The end. Learn everything yourself." But of course he does try to teach, but nobody in class knows whats going on. So I've have found a few good web sites on C++ and have a book on C++, but I'm only starting to learn arrays. I have the simple basic for C++, but still, I have no idea on how to use arrays. So while I'm trying to learn it, I taught that may be I could post here and ask for advices and a bit of lessons. Could anyone give me a simple example of a code using arrays? How about, arranging numbers from smallest to biggest? I will scan my mock test and post it here later, so that you guys have a better Idea of the test. And since its an open book test, we are allowed to have notes during the test, whether on paper or even on the internet. So would it be okay if I log on this site during the test? But no cheating of course... May be to help me out a bit?
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11-25-2006, 01:31 PM	#3
therabidwombat Registered User Join Date: Oct 2006 Posts: 16	I think that if he can't understand arrays at this point, then sorting algorithms may be a little beyond his current abilities. For arrays, it's really quite simple if you understand variables. All that an array is is a variable. so what makes an array different, you ask? Well, for one thing, arrays are more than one variable. Here's the example that I've seen used numerous times when describing arrays: Suppose that you have six numbers. Each one is the id of an object. So we'd have Code: int id1, id2, id3, id4, id5, id6; id1 = 0; id2 = 1; id3 = 5; id4 = 7; id5 = 2; id6 = 4; Now, as you can see, all of these numbers are related, yet they're all seperate variables. But if you use an array, you can do this: Code: int id[6]; id[0] = 0; id[1] = 1; id[2] = 5; id[3] = 7; id[4] = 2; id[5] = 4; the [n] area of each array is called it's 'indice'. Note that arrays start at an indice zero; as such, when you declare an array of length 6 (by going int id[6]), you end up with an array with indices from zero to five. What's the point of this? At first, there doesn't seem to be much of any. However, there are several uses, one of the most common uses is that arrays and for loops are built for each other. Instead of having to do: Code: cout << id1 << "\n"; cout << id2 << "\n"; coud << id3 << "\n" ... you could do Code: for(int i = 0; i < 6; i++) cout << id[i] << "\n";
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11-25-2006, 02:18 PM	#4
dwks Frequently Quite Prolix Join Date: Apr 2005 Location: Canada Posts: 7,698	There's a tutorial on arrays, I don't know if you've seen it: http://www.cprogramming.com/tutorial/lesson8.html Basically, an array is a convenient name for many different variables as the previous poster has indicated. __________________ dwk Seek and ye shall find. quaere et invenies. "Simplicity does not precede complexity, but follows it." -- Alan Perlis "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra "The only real mistake is the one from which we learn nothing." -- John Powell Other boards: DaniWeb, TPS Unofficial Wiki FAQ: cpwiki.sf.net My website: http://dwks.theprogrammingsite.com/ Projects: codeform, xuni, atlantis, nort, etc.
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11-25-2006, 04:48 PM	#6
[Z-D] Registered User Join Date: Oct 2006 Posts: 37	Wait, wait.... May be I got it. Is this how you input the values? Code: int main(); { int grades[10] for (int i = 0; i < 4; 4; i++) { cout << "Enter 10 grades: "; cin >> grades[i]; } Did I get it right?
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11-25-2006, 04:56 PM	#7
Desolation Registered User Join Date: May 2006 Posts: 894	Your for() loop is wrong, it should read for(int i = 0; i < 10; i++). There also lacks a closing brace and you have an extra semi-colon after int main(). Oh, and you lack a semi-colon after int grades[10]; __________________ www.atempsperdu.net/forum/ www.atempsperdu.net/site/en/
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11-25-2006, 05:59 PM	#8
[Z-D] Registered User Join Date: Oct 2006 Posts: 37	Oh yeah... mistakes. Thanks. So it should be: Code: int main(); { int grades[10]; for(int i = 0; i < 10; i++); { cout << "Enter 10 grades: "; cin >> grades[i]; } ... ... ... return 0; } So, about the median thingy... How did they get sorted? I don't get it...
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11-25-2006, 06:30 PM	#9
swgh Its hard... But im here Join Date: Apr 2005 Location: England Posts: 1,467	>int main(); Still got a semi-colon here __________________ I'm just trying to be a better person - My Name Is Earl
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11-26-2006, 09:45 AM	#12
Desolation Registered User Join Date: May 2006 Posts: 894	1. You were wrong when you said the sorting was done by printArray(). 2. No, changing j = 1 to j = 0 will crash your program. Try to find why, as an exercise. 3. Not changing i >= 0 will simply leave you with an useless for() loop executed. You have to change it to i >= 1 to get rid of it because then when i equals 1, the second for() loop will get executed as well (since it is executed for j <= i). __________________ www.atempsperdu.net/forum/ www.atempsperdu.net/site/en/
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11-27-2006, 10:36 AM	#14
elad Registered User Join Date: Mar 2002 Posts: 1,595	>>What are the mistakes in this code? After a quick look through, there should be a { between the following two lines: Code: for ( rating = 1; rating <= 9; rating++ ) cout << setw( 8 ) << rating << setw( 11 ) I'd prefer this: Code: for ( int h = 1; h <= freq[ rating ]; h++ ) cout << ''; cout << '\n'; look like this: Code: for ( int h = 1; h <= freq[ rating ]; h++ ) cout << ''; cout << '\n'; to be more clear in the intention, but it's not wrong as posted and the indentation may be a problem with the board and not the author. >>Would this work Run it and find out. The big problem I see is you are sorting with every input, which is time intensive. Moving these two lines out of the loop may be better. cout << "Your sorted grades are: "; bubbleSort(int numbers[], int array_size); __________________ You're only born perfect.
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