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Bubble Sort with an array filled with classes.

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Join Date: Oct 2007
Posts: 25
#1: Nov 30 '07
Hello everyone, I am familiar with a normal bubble sort when dealing with an array of number but I am unsure as how to implement a sort when I have an array that is filled with classes which hold multiple values.

I need to make a bubble sort that reaches into an array called Tree[100] which has in each storage location a class called Christmas Tree which have the values Species, Height, trunkDiameter, and costPerFoot. The sort will need to sort the different trees by species (which is a string) and then by costPerFoot (a double).

Regular bubble sort:
Expand|Select|Wrap|Line Numbers
  1. void bubblesort (int a[], int n) // n = SIZE;
  2. {
  3.      bool sorted = false;
  4.      for (int i = 0; i < n-1 && !sorted; i++)
  5.      {
  6.          sorted = true;
  7.          for (int j = 0; j < (n-1-i); j++)
  8.          {
  9.              if (a[j] > a[j+1])
  10.              {
  11.                       swap (a[j], a[j+1]);
  12.                       sorted = false;
  13.              }
  14.          }
  15.      }
  16. }
Any ideas?

Newbie
  
Join Date: Oct 2007
Posts: 25
#2: Nov 30 '07

re: Bubble Sort with an array filled with classes.

I had an idea. I have a function called getSpecies() and getCost() which simply returns the values found in whatever array area your in. Could I...

Expand|Select|Wrap|Line Numbers
  1. void bubblesort (char a[], int n) // n = SIZE;
  2. {
  3.      bool sorted = false;
  4.      for (int i = 0; i < n-1 && !sorted; i++)
  5.      {
  6.          sorted = true;
  7.          for (int j = 0; j < (n-1-i); j++)
  8.          {
  9.              if ( a[j].getSpecies() > a[j+1].getSpecies() )
  10.              {
  11.                       swap (a[j], a[j+1]);
  12.                       sorted = false;
  13.              }
  14.          }
  15.      }
  16. }
  17.  
  18.  
Ganon11's Avatar
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Location: New York, United States of America
Posts: 3,428
#3: Nov 30 '07

re: Bubble Sort with an array filled with classes.

That idea will work...if you pass an array of this class/struct. Right now you are passing in a character array, then trying to use a class function on it. Characters are not classes. You will want to pass a Tree[] to your function and sort that.

Even better, overload the < and > operators for Tree. You can compare names first - if the names are the same, you can compare some other attribute.

This will allow you to write a generalized bubblesort using templates:

Expand|Select|Wrap|Line Numbers
  1. template <class Comparable>
  2. void bubble_sort(Comparable[] array, int size);
Newbie
  
Join Date: Oct 2007
Posts: 25
#4: Nov 30 '07

re: Bubble Sort with an array filled with classes.

Quote:

Originally Posted by Ganon11

That idea will work...if you pass an array of this class/struct. Right now you are passing in a character array, then trying to use a class function on it. Characters are not classes. You will want to pass a Tree[] to your function and sort that.

Even better, overload the < and > operators for Tree. You can compare names first - if the names are the same, you can compare some other attribute.

This will allow you to write a generalized bubblesort using templates:

Expand|Select|Wrap|Line Numbers
  1. template <class Comparable>
  2. void bubble_sort(Comparable[] array, int size);

I havnt worked with templates so im a bit confused. Would it look something like this?

template <class Tree>
void bubble_sort(Tree[], int size);
Newbie
  
Join Date: Oct 2007
Posts: 25
#5: Nov 30 '07

re: Bubble Sort with an array filled with classes.

Im afraid that may be too difficult for my experience with C++. Anyway this is what im up to:

Expand|Select|Wrap|Line Numbers
  1. void bubblesort (??? a[], int n); // Prototype
  2.  
  3. void bubblesort (Tree[], int n) // n = SIZE;
  4. {
  5.      bool sorted = false;
  6.      for (int i = 0; i < n-1 && !sorted; i++)
  7.      {
  8.          sorted = true;
  9.          for (int j = 0; j < (n-1-i); j++)
  10.          {
  11.              if ( a[j].getSpecies() > a[j+1].getSpecies() )
  12.              {
  13.                       swap (a[j], a[j+1]);
  14.                       sorted = false;
  15.              }
  16.          }
  17.      }
  18. }
Is there a data type or something I could do in order for it to work?
Ganon11's Avatar
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Location: New York, United States of America
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#6: Nov 30 '07

re: Bubble Sort with an array filled with classes.

Quote:

Originally Posted by midknight5

Im afraid that may be too difficult for my experience with C++. Anyway this is what im up to:

Expand|Select|Wrap|Line Numbers
  1. void bubblesort (??? a[], int n); // Prototype
  2.  
  3. void bubblesort (Tree[], int n) // n = SIZE;
  4. {
  5.      bool sorted = false;
  6.      for (int i = 0; i < n-1 && !sorted; i++)
  7.      {
  8.          sorted = true;
  9.          for (int j = 0; j < (n-1-i); j++)
  10.          {
  11.              if ( a[j].getSpecies() > a[j+1].getSpecies() )
  12.              {
  13.                       swap (a[j], a[j+1]);
  14.                       sorted = false;
  15.              }
  16.          }
  17.      }
  18. }
Is there a data type or something I could do in order for it to work?

We're closer here. First, I'll explain about templates.

Templates basically allow you to write a generalized function. So, if I had a function:

Expand|Select|Wrap|Line Numbers
  1. template <class T>
  2. T addTwo(T& objectOne, T& objectTwo) {
  3.    return objectOne + objectTwo;
  4. }
I can now call addTwo on any class or type that the + operator makes sense. So, for instance, I could call it in this way:

Expand|Select|Wrap|Line Numbers
  1. int x = addTwo<int>(5, 20);
Note the <int> - this tells the function what class or type I am filling in for the template. So, by putting the <int> there, I've effectively changed this function to

Expand|Select|Wrap|Line Numbers
  1. int addTwo(int& objectOne, int& objectTwo) {
  2.    return objectOne + objectTwo;
  3. }
But that change only lasts for that one call. I can still later say

Expand|Select|Wrap|Line Numbers
  1. double y = addTwo<double>(3.5, 12.02);
and it will work. I can even add classes that have a + operator - for instance, if I defined a Vector class, and gave it a + operator, I could say

Expand|Select|Wrap|Line Numbers
  1. Vector resultant = addTwo<Vector>(firstVec, secondVec);
All three of these examples work.

Now, in your case, you are writing a bubblesort function. When sorting, generally you only need to know if an object is less than or greater than another object. You don't care what type the objects are, as long as you can compare them - they could be numbers, they could be Trees, they could be Apple Pies, they could be anything, as long as you can compare them. You put this into code by using a template, and when it comes time to compare one object to another, use the '<' operator. You can assume that whatever object you are sorting has the '<' operator, because it makes no sense to sort an object that cannot be sorted.

Now that you are using templates, you can write a generic bubble sort function. When writing it, forget the fact that you are working with Trees. Just think about sorting some general object - it's common to think about sorting integers, as it's easy to visualize and see whether integer A is larger than or smaller than integer B. Once you have your bubblesort function working, then you have one more thing to worry about - does your Tree class overload the '<' operator?

In order to do so, you need to provide the following function in your Tree class:

Expand|Select|Wrap|Line Numbers
  1. bool operator<(Tree& rightHandSide) const;
The body of this function will determine if the current tree is less than the rightHandSide tree, and if so, return true. Otherwise, it must return false. This is where you will compare the Tree's species type and anything else you wanted to sort by.
Newbie
  
Join Date: Oct 2007
Posts: 25
#7: Nov 30 '07

re: Bubble Sort with an array filled with classes.

Im so sorry but some of that I dont understand, im only in Intro to C++ and we are at the final stage of our learning for the semester so vectors and the like I havnt gotton to yet. I did however find a way that it will work but I encounter a problem that maybe someone can help me with. The point of this program is to open up a file with an unknown number of Tree[]s in it then read the lines and put the correct data into the correct part in the array in the class.

Example data

Douglas Fir
3.38
4.38
12.29
Ponderous Pine
11.37
5.45
11.5

So I have a for loop that I thought would read each part and put it into its correct area:

Expand|Select|Wrap|Line Numbers
  1. for (int i = 0; inData; i++)
  2.     {
  3.         inData >> s;
  4.  
  5.         inData.ignore(MAX, '\t');
  6.         inData >> h;
  7.  
  8.         inData.ignore(MAX, '\t');
  9.         inData >> tD;
  10.  
  11.         inData.ignore(MAX, '\t');
  12.         inData >> cPF;
  13.  
  14.         inData.ignore(MAX, '\t');
  15.  
  16.         Tree[i].setSpecies(s);
  17.         Tree[i].setHeight(h);
  18.         Tree[i].setTrunkDiameter(tD);
  19.         Tree[i].setCostPerFoot(cPF);
  20.  
  21.         count++;
  22.     }
But whenever I check my program it only gives me the output of my constructor function so its as if the programs cursor is not in the right location or not doing something right. This is last problem I can find so help is appreciated!
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Location: North Bend Washington USA
Posts: 5,382
#8: Nov 30 '07

re: Bubble Sort with an array filled with classes.

Quote:

Originally Posted by Ganon11

In order to do so, you need to provide the following function in your Tree class:


Code: ( cpp )
bool operator<(Tree& rightHandSide) const;

There is also the option of writing the operator< as a regular global function:
Expand|Select|Wrap|Line Numbers
  1. bool operator<(Tree& lefthandside, Tree& rightHandSide);
  2.  
In your sort you should, be able to:
Expand|Select|Wrap|Line Numbers
  1. if ( a[j] < a[j+1] )
  2. {
  3.  
  4. }
  5.  
Newbie
  
Join Date: Oct 2007
Posts: 25
#9: Nov 30 '07

re: Bubble Sort with an array filled with classes.

Ok, ive made some progress and im down to my last two problems. First off, after ive opened up the file and sorted my trees by Species, I want to sort them ALSO by cost. but I am unsure of how to do that.

Current bubblesort for species:

Expand|Select|Wrap|Line Numbers
  1. void bubblesort ( ChristmasTree a[],int n) // n = SIZE;
  2. {
  3.      bool sorted = false;
  4.      for (int i = 0; i < n-1 && !sorted; i++)
  5.      {
  6.          sorted = true;
  7.          for (int j = 0; j < (n-1-i); j++)
  8.          {
  9.              if ( a[j].getSpecies() > a[j+1].getSpecies() )
  10.              {
  11.                       swap (a[j], a[j+1]);
  12.                       sorted = false;
  13.              }
  14.  
  15.  
  16.  
  17.          }
  18.      }
  19. }
The last problem is with outputting the trees to the screen. I have a for loop that outputs them like so:
Expand|Select|Wrap|Line Numbers
  1. for (int i = 0; i < count - 1; i++)
  2.      {
  3.          cout << fixed                   << setprecision(2) 
  4.               << Tree[i].getSpecies()    << endl;
  5.          cout << Tree[i].getHeight()     << endl;
  6.          cout << Tree[i].calculateCost() << endl;
  7.  
  8.               total += Tree[i].calculateCost();
  9.      }
  10.  
  11.      cout << "There are " << count << " trees listed." << endl;
  12.      cout << "The average price of a tree is " << total/count << endl;
But in the actual output I get my constructor listed like 20 times before it starts listing the other trees. whats up with that?

Ex.

Expand|Select|Wrap|Line Numbers
  1. Blue Spruce
  2. 8.36
  3. 188.10
  4. Blue Spruce
  5. 9.98
  6. 224.55
  7. Douglas Fir
  8. 3.38
  9. 41.41
  10. Douglas Fir
  11. 4.88
  12. 59.78
  13. Douglas Fir
  14. 8.59
  15. 105.23
  16. Fraser Fir
  17. 6.00
  18. 77.70
  19. Fraser Fir
  20. 6.00
  21. 77.70
  22. Fraser Fir
  23. 6.00
  24. 77.70
  25. Fraser Fir
  26. 6.00
  27. 77.70
  28. Fraser Fir
  29. 6.00
  30. 77.70
  31. Fraser Fir
  32. 6.00
  33. 77.70
  34.  
  35. Ponderosa Pine
  36. 11.37
  37. 130.75
  38. Ponderosa Pine
  39. 12.83
  40. 147.54
  41. Ponderosa Pine
  42. 11.09
  43. 127.53
  44. Ponderosa Pine
  45. 5.58
  46. 64.17
  47. Ponderosa Pine
  48. 6.81
  49. 78.31
  50. Ponderosa Pine
  51. 4.12
  52. 47.38
Ganon11's Avatar
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Location: New York, United States of America
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#10: Nov 30 '07

re: Bubble Sort with an array filled with classes.

Do you want to sort separately i.e. have two separate functions - one that sorts by cost, the other that sorts by species? This is fairly simple - you can copy and paste your code, and change getSpecies to getCost.

Or do you want them sorted by species, and each subset of species sorted by cost? To do this, in your sort, consider when you would need to sort by cost - only when the species is the same, right? Then you can add another possibility to your if...statement in the inner loop.
Newbie
  
Join Date: Oct 2007
Posts: 25
#11: Nov 30 '07

re: Bubble Sort with an array filled with classes.

Quote:

Originally Posted by Ganon11

Do you want to sort separately i.e. have two separate functions - one that sorts by cost, the other that sorts by species? This is fairly simple - you can copy and paste your code, and change getSpecies to getCost.

Or do you want them sorted by species, and each subset of species sorted by cost? To do this, in your sort, consider when you would need to sort by cost - only when the species is the same, right? Then you can add another possibility to your if...statement in the inner loop.

When you say add another possiblity do you mean add something like:

if(a[j].getSpecies() > a[j+1].getSpecies() || a[j].calculateCost() > a[j+1].calculateCost())

or add another if statement?
Ganon11's Avatar
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Join Date: Oct 2006
Location: New York, United States of America
Posts: 3,428
#12: Nov 30 '07

re: Bubble Sort with an array filled with classes.

I mean you should either say:

Expand|Select|Wrap|Line Numbers
  1. if (a[j].species > a[j+1].species OR (a[j] and a[j+1] have the same species AND a[j].cost > a[j+1].cost)) {
  2.    // swap...blah blah blah.
  3. }
or you should say

Expand|Select|Wrap|Line Numbers
  1. if (a[j].species > a[j+1].species) {
  2.    // swap...blah blah blah
  3. } else if (a[j] and a[j+1] have the same species AND a[j].cost > a[j+1].cost) {
  4.    // swap...blah blah blah
  5. }
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Location: North Bend Washington USA
Posts: 5,382
#13: Dec 1 '07

re: Bubble Sort with an array filled with classes.

You might consider a comparator function. Here you write a function that does the correct comparison and pass the address of the function to the bubble sort as an argument.

You would write a function that takes two Tree& arguments and you pass a pointer to this function to the bubble sort as a function pointer. Inside the sort you call the function by using the function pointer. The sort will then produce the sequence based on that call.

Assume you have written:
Expand|Select|Wrap|Line Numbers
  1. bool Seq1(Tree& left, Tree& right);            //sorts ascending
  2. bool Seq2(Tree& left, Three& right);          //sorts descending
  3. bool Seq3(Tree&left, Tree& right);            //sorts by SPECIES ascending
  4. etc...
  5.  
Your sort:
Expand|Select|Wrap|Line Numbers
  1. void bubblesort (int a[], int n, bool (*Compare)(Tree&, Tree&))
  2. {
  3.        if (Compare(a[i], a[i+1])
  4.        {
  5.                //a[i] is "less" than a[i+1]
  6.        }
  7. }
  8.  
Then you can call the sort to get three different sequences:
Expand|Select|Wrap|Line Numbers
  1. bubblesort(a, 100, Seq1);
  2. bubblesort(a, 100, Seq2);
  3. bubblesort(a, 100, Seq3);
  4.  
To use your operator< you could:
Expand|Select|Wrap|Line Numbers
  1. bool Seq4(Tree& left, Tree& right)
  2. {
  3.     return left < right:
  4. }
  5.  
and to sort in the reverse sequence (>=):
Expand|Select|Wrap|Line Numbers
  1. bool Seq4(Tree& left, Tree& right)
  2. {
  3.     if (left < right)
  4.      {
  5.            return false;
  6.      }
  7.      return true;
  8.  
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