Procedure to sort a two dimensional int array depending on column

Question

The array I have before and how we want it after the sorting:

Before:

Box    Weight    Priority
1       50          5
2       30          8
3       90          6
4       20          7  
5       80          9

After:

Box    Weight    Priority
3       90          6
5       80          9
1       50          5
2       30          8
4       20          7

We work in the int matrix:

data= new int[BoxNumber][3];

The sorting is based in the second column Weight. I am looking for a procedure that sorts the data array.

 public void sortC(int[][] temp)
{
    if (temp.length >= 2)
    {
        for (int i = 1; i <= temp.length - 1; i++)
        {
            int[] hold = temp[i];
            int[] holdP = temp[i-1];

            int j = i;

            while (j > 0 && hold[1] < holdP[1]) // 1 represents the reference of sorting
            {
                hold = temp[j];
                holdP = temp[j-1];

                temp[j] = holdP;
                temp[j-1] = hold;

                j--;
            }
        }
    }
}

 sortC(data);

I tried this one, but unfortunately it doesn't give a right sorting I couldn't figure out the pickle.

johnchen902 · Accepted Answer · 2016-08-30 12:21:22Z

10

Use java.util.Arrays.sort with a custom Comparator.

int[][] temp = { { 1, 50, 5 }, { 2, 30, 8 }, { 3, 90, 6 },
        { 4, 20, 7 }, { 5, 80, 9 }, };
Arrays.sort(temp, new Comparator<int[]>() {
    @Override
    public int compare(int[] o1, int[] o2) {
        return Integer.compare(o2[1], o1[1]);
    }
});

As shmosel mentioned below, with Java 8, you can use:

Arrays.sort(temp, Comparator.comparingInt(arr -> arr[1]));

edited Aug 30, 2016 at 12:21

answered Aug 14, 2013 at 13:29

johnchen902

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4 Comments

Ghassen Bellagha Over a year ago

the method u gave Arrays.sort works perfectly. Could you please mention some comments to explain the method for me because am not good into Comparator and Arrays.sort tools ? And Thank Your for your help

johnchen902 Over a year ago

@GhassenBellagha Java docs: Arrays.sort

shmosel Over a year ago

In Java 8, Arrays.sort(temp, Comparator.comparingInt(arr -> arr[1]));

johnchen902 Over a year ago

@shmosel Thanks. Never revisited this post.

Tala · Accepted Answer · 2013-08-14 13:23:03Z

2

You can do this instead of writing your own sorting algorithm:

int[][] n = new int[10][];
//init your array here

List<int[]> ints = Arrays.asList(n);
Collections.sort(ints, new Comparator<int[]>() {
    @Override
    public int compare(int[] o1, int[] o2) {
        return o1[1] - o2[1]; // compare via second column
    }
});

and if you want make it array again:

int[][] result = ints.toArray(n);

answered Aug 14, 2013 at 13:23

Tala

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1 Comment

Ghassen Bellagha Over a year ago

is there any other way where we could correct the procedure i mentioned ? Cause am not good into lists and collections .. ?

Purva · Accepted Answer · 2021-02-01 01:07:42Z

1

Arrays.sort(boxTypes, (a, b) -> b[1] - a[1]);

or Using a priority queue

PriorityQueue<int[]> queue = new PriorityQueue<>((a, b)->b[1] - a[1]);

answered Feb 1, 2021 at 1:07

Purva

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