sort 2D int array JAVA

Question

I have one 2 dimensional array It's an array with 7 int in line and more lines.

int[][] new arr=new[7][100];

number in line is ranked.

I need a ranked array.

for example

9 4 15 22 32 47 50
1 5 9 12 19 25 36
22 23 25 29 36 55 99
1 5 11 12 19 25 36

after sort

1 5 9 12 19 25 36
1 5 11 12 19 25 36
9 4 15 22 32 47 50
22 23 25 29 36 55 99

You may want to transpose your array first, so that each element is one line (i.e. int[100][7] instead of int[7][100]). Here is an example http://introcs.cs.princeton.edu/java/14array/Transpose.java.html — Tesseract, Feb 11 '17 at 22:03

score 1 · Accepted Answer · answered Feb 11 '17 at 22:00

1

The simple approach to solved this problem is transform your 2D array into List of 1D array.

List<int[]> list = new ArrayList<int[]>();
// add logic to transform your 2D array here

Then you can use Collections.sort() with custom Comparator function.

Collections.sort(list, new Comparator<int[]>() {
    public int compare(int []a,int []b) {
        for(int i=0;i<6;i++)
            if(a[i]!=b[i]) return a[i]-b[i];
        return a[6] - b[6];
    }
});

answered Feb 11 '17 at 22:00

algojava

743
4
9

I don't know how use this code in my program. How use arraylist when i have int[][] – user7495572 Feb 11 '17 at 22:03
i left that part for you to practice :). – algojava Feb 11 '17 at 22:07
Instead of using an ArrayList you could also leave it as an array and sort it with Arrays.sort. You just have to turn your `int[7][100]` into an `int[100][7]` first. – Tesseract Feb 11 '17 at 22:07
Ok I have int[][] new arr[100][7] what now? – user7495572 Feb 11 '17 at 22:10
@SpiderPig: Arrays.sort() only works for 1D array, he want to compare the 7 value from each row. – algojava Feb 11 '17 at 22:11
1

`Collections.sort` also just works for one dimensional collections. Doesn't matter though. Just use the comparator from your example. – Tesseract Feb 11 '17 at 22:12
and how use comparator in example? – user7495572 Feb 11 '17 at 22:14
Use algojava's code and replace `Collections.sort` with `Arrays.sort` and `list` with `arr`. – Tesseract Feb 11 '17 at 22:15
if you decide to using 2D array, then you need to change Collections.sort() to Arrays.sort() – algojava Feb 11 '17 at 22:23

score 0 · Answer 2 · answered Jun 04 '17 at 08:01

I would do something like this,or something similar:

I saw something similar in Stack Overflow: https://stackoverflow.com/a/15452462/8024829.

 double[][] array= {
   {1, 5},
   {13, 1.55},
   {12, 100.6},
   {12.1, .85} };

   java.util.Arrays.sort(array, new java.util.Comparator<double[]>() {
       public int compare(double[] a, double[] b) {
           return Double.compare(a[0], b[0]);
       }
   });

score 0 · Answer 3 · answered Feb 14 '22 at 09:18

0

You can try this simple expression:

Arrays.sort(A, (a, b) -> a[0] - b[0]);

answered Feb 14 '22 at 09:18

Joe

326
3
11

sort 2D int array JAVA

3 Answers3