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Sort 2d array (Read 1859 times)
DA.B
Sort 2d array
Nov 27th, 2008, 6:23pm  
Hi board,
I have this 2d array of rgb values.
I like to sort them from the highest rgb[i][2] value to the lowest. Does anyone can help me, because I don´t know the correct sort() syntax for 2d arrays...

float[][] rgb = new float[3][3];
rgb[0][0] = 100.0;
rgb[0][1] = 100.0;
rgb[0][2] = 255.0;

rgb[1][0] = 12.0;
rgb[1][1] = 45.0;
rgb[1][2] = 200.0;

rgb[2][0] = 111.0;
rgb[2][1] = 12.0;
rgb[2][2] = 251.0;

for(int i = 0; i < rgb.length; i++) {
 fill(rgb[i][0], rgb[i][1], rgb[i][2]);
 rect(20+i*20,20,20,20);
 println( "r= "+rgb[i][0] + ", g= " + rgb[i][1] + ", b= " + rgb[i][2]);
}
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sw01
Re: Sort 2d array
Reply #1 - Nov 27th, 2008, 9:14pm  
I think there are two problems here: one is the sorting of 2D matrix, and another is the overall goal to the code.

You may have to look for or implement your own 2D matrix sorting algorithm, which would be kind of painful in this environment (I may be wrong - anyone?).

For sorting RGB values: You may want to create an RGB type and handle that as an object, then sort that with a comparator that uses its blue value.  So it may look like:


class Rgb{
 Float r, g, b;
 
 Rgb(Float r, Float g, Float b){
   this.r = r;
   this.g = g;
   this.b = g; //this.g = b;
 }
}

class RgbBlueComparator implements Comparator{
public int compare(Object o1, Object o2) {
               Float i = ((Rgb)o1).b -  ((Rgb)o2).b;
return i.intValue();
}
}


Again, use of generics will make the second chunk a lot more readable, so you may want to implement this in a .java file.
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« Last Edit: Nov 28th, 2008, 7:54pm by sw01 »  
 
DA.B
Re: Sort 2d array
Reply #2 - Nov 28th, 2008, 12:22pm  
Thank you sw01!
I see what the problem is and this will help me. So I will try out to solve the problem with your way.
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PhiLho 
Re: Sort 2d array
Reply #3 - Nov 28th, 2008, 1:25pm  
Aah, I wondered why you used a Comparator instead of making RGB implementing Comparable.
Found a good explanation at java.util.Comparable vs java.util.Comparator... Smiley
Of course, your method is the best in this case, because one might want to implement RgbRedComparator and RgbGreenComparator as well.
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eskimoblood
Re: Sort 2d array
Reply #4 - Nov 28th, 2008, 4:26pm  
Toxi posts a sorting algorythm for colors long time ago:

http://www.toxi.co.uk/blog/2006/04/colour-code-snippets.htm
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Andreas Köberle {eskimoblood}
222550793  
sw01
Re: Sort 2d array
Reply #5 - Nov 28th, 2008, 7:52pm  
Hi,

Sorry, I found an embarrassing bug. The class Rgb should be:

Rgb{
 Float r, g, b;
 
 Rgb(Float r, Float g, Float b){
   this.r = r;
   this.g = g;
   this.b = b;
 }
}

Instead of // this.g = b;

Teaches me a lesson: I shouldn't be using single letter variables.  :)

Just in case cut and paste is used.



< PhiLho: Thank you for the followup.

I should have explained that this was intended to be used with Collections.sort(List l, Comparator c), where List can be ArrayList.  That's what happens when one talks to machines for too long...
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brEnergy
Re: Sort 2d array
Reply #6 - Jan 14th, 2010, 6:33am  
Code for sorting 2d array.  Just change the if statement in the for loop to whatever item you want to sort on.

boolean sorted=false;
 do{
   sorted=true;
   for(index=0;index<tempPlantCounter-1;index++){
     if(tempPlant[7][index]>tempPlant[7][index+1]){  //if plant before costs more, swap places
      float bigSummerCapacity = tempPlant[0][index];
      float bigHeatRate = tempPlant[1][index];
      float bigVom = tempPlant[2][index];
      float bigFom = tempPlant[3][index];
      float bigCapacityFactor = tempPlant[4][index];
      float bigPolicyCost = tempPlant[5][index];
      float bigEnergyCost = tempPlant[6][index];
      float bigTotalCost = tempPlant[7][index];
     
      int i;
      for(i=0;i<8;i++){
       tempPlant[i][index]=tempPlant[i][index+1];
      }
      //tempPlant[5][index]=tempPlant[5][index+1];
      //tempPlant[6][index]=tempPlant[6][index+1];
      //tempPlant[7][index]=tempPlant[7][index+1];
      tempPlant[0][index+1]=bigSummerCapacity;
      tempPlant[1][index+1]=bigHeatRate;
      tempPlant[2][index+1]=bigVom;
      tempPlant[3][index+1]=bigFom;
      tempPlant[4][index+1]=bigCapacityFactor;
      tempPlant[5][index+1]=bigPolicyCost;
      tempPlant[6][index+1]=bigEnergyCost;
      tempPlant[7][index+1]=bigTotalCost;
      sorted=false;
     }
   }
 }
 while(sorted==false);
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PhiLho 
Re: Sort 2d array
Reply #7 - Jan 14th, 2010, 6:39am  
You re-invent a sort algorithm, not the fastest either...
And when you start to have an array of values mapping to various information, as the temporary variable names implies, you should start looking into classes. Smiley
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jonobrone
Re: Sort 2d array
Reply #8 - Feb 17th, 2010, 3:23am  
brEnergy, could you explain that a little more?

It does this?

from
Code:

String[][] databaseToArray = {
  //{"Name", "Channel", "Description", "Amount", "isReady"},
    {"John", "Nick",    "likes",	 "2",	"yes"    },
    {"Drew", "MTV",     "dislikes",    "4",	"no"     },
    {"Fred", "CNN",     "okay",	  "3",	"no"     },
    {"Beth", "Fox",     "valid",	 "1",	"yes"    }
};


to
Code:

String[][] reorganizedArray = {
  //{"Name", "Channel", "Description", "Amount", "isReady"},
    {"Beth", "Fox",     "valid",	 "1",	"yes"    },
    {"John", "Nick",    "likes",	 "2",	"yes"    },
    {"Fred", "CNN",     "okay",	  "3",	"no"     },
    {"Drew", "MTV",     "dislikes",    "4",	"no"     }
};
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