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Thread: sorting only 1 column of 2D array

  1. #1
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    Default sorting only 1 column of 2D array

    hi.. i am trying to sort my 2D array such that only the 2nd column get sorted.. i tried to use Arrays.sort(arr[a]) but it seem to sort the whole array

    example of what i want:
    before sort
    a[0][0]= 9 a[1][0] = 50
    a[0][1]= 5 a[1][1] = 5
    a[0][2]= 3 a[1][2] = 78
    a[0][3]= 6 a[1][3] = 23
    a[0][4]= 2 a[1][4] = 67

    aft sort
    a[0][0]= 2 a[1][0] = 5
    a[0][1]= 3 a[1][1] = 23
    a[0][2]= 5 a[1][2] = 50
    a[0][3]= 6 a[1][3] = 67
    a[0][4]= 9 a[1][4] = 78

    the code i m using now
     for (int i=0;i<dist.length;i++)
            {
                Arrays.sort(dist[i]);
            }

    output of current code:
    before sort
    a[0][0]= 9 a[1][0] = 50
    a[0][1]= 5 a[1][1] = 5
    a[0][2]= 3 a[1][2] = 78
    a[0][3]= 6 a[1][3] = 23
    a[0][4]= 2 a[1][4] = 67

    aft sort
    a[0][0]= 2 a[1][0] = 9
    a[0][1]= 3 a[1][1] = 23
    a[0][2]= 5 a[1][2] = 50
    a[0][3]= 5 a[1][3] = 67
    a[0][4]= 6 a[1][4] = 78


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: sorting only 1 column of 2D array

    Can you post the definition of an array to sort as java code for testing?
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: sorting only 1 column of 2D array

     double[][] a1 = new double[][] {{2.5,3.6,0.7,0.01},{0.85,1.32,0.20,0.992}};

    based on this the output after sorting should be
    a1[0][0] = 0.01 a1[1][0] = 0.20
    a1[0][1] = 0.7 a1[1][0] = 0.85
    a1[0][2] = 2.5 a1[1][0] = 0.992
    a1[0][3] = 3.6 a1[1][0] = 1.32

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: sorting only 1 column of 2D array

    When I execute this code:
          double[][] dist = new double[][] {{2.5, 3.6, 0.7, 0.01},{0.85, 1.32, 0.20, 0.992}};
          System.out.println("B="+Arrays.deepToString(dist));
          for (int i=0;i<dist.length;i++)
            {
                Arrays.sort(dist[i]);
            }
          System.out.println("A="+Arrays.deepToString(dist));
    I get this printed:
    B=[[2.5, 3.6, 0.7, 0.01], [0.85, 1.32, 0.2, 0.992]]
    A=[[0.01, 0.7, 2.5, 3.6], [0.2, 0.85, 0.992, 1.32]]
    It looks sorted to me.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: sorting only 1 column of 2D array

    Quote Originally Posted by Norm View Post
    When I execute this code:
          double[][] dist = new double[][] {{2.5, 3.6, 0.7, 0.01},{0.85, 1.32, 0.20, 0.992}};
          System.out.println("B="+Arrays.deepToString(dist));
          for (int i=0;i<dist.length;i++)
            {
                Arrays.sort(dist[i]);
            }
          System.out.println("A="+Arrays.deepToString(dist));
    I get this printed:

    It looks sorted to me.
    Weird... As stated in my first post. I tried your method and did not get your result. Will check where I did wrong

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    Default Re: sorting only 1 column of 2D array

    thanks for all the help... think the error i 1st encounter is my stupid self trying to display a shorter version of my array.. did not realise that the value is hidden in the array index i did not wan to be displayed out...

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