Sort 2D array rows

Question

I have 2D array which I need to sort it's rows only, and I have done with this code:

double[][] arr = initArray();

    for (int row = 0; row < arr.length; row++) {
        int index = row;
        double minVal = arr[row][0];
        for (int column = 0; column < arr[row].length; column++) {

            if (arr[row][column] < minVal) {
                minVal = arr[row][column];
                index = column;
            }

        }


        arr[row][index] = arr[row][0];
        arr[row][0] = minVal;

    }

Sample input:

{{0.15, 0.875, 0.375},
 {0.55, 0.005, 0.225},
 {0.30, 0.12, 0.4}}

Expect out put:

0.15 0.375 0.875 
0.005 0.225 0.55 
0.12 0.3 0.4

What I get:

0.15 0.875 0.375 
0.005 0.55 0.225 
0.12 0.3 0.4

2d array is array of arrays `{ {...}, {...}, {...} }`. Your current code doesn't sort internal arrays, it is searching for minimum in each row and moves it at start of that row. Try to think of way to sort 1d array and then apply it to each row. — Pshemo, Nov 08 '17 at 00:19
@jontro thanks for pointing that, but it's not duplication here, I said `rows`. — , Nov 08 '17 at 00:37

Armin Suljovikj · Answer 1 · 2017-11-08T00:41:39.490

1

You can use the Arrays.sort(); function from the java.util.Arrays class to sort each row in your 2d Array.

 for (double[] innerArray: outerArray) {
     Arrays.sort(innerArray);
 }

EDIT: Here is the entire example:

double[][] outerArray = {
     {
         0.15,
         0.875,
         0.375
     },
     {
         0.55,
         0.005,
         0.225
     },
     {
         0.30,
         0.12,
         0.4
     }
 };


 for (double[] innerArray: outerArray) {
     Arrays.sort(innerArray);
 }


 for (int i = 0; i < outerArray.length; i++) {

     for (int j = 0; j < outerArray.length; j++) {

         System.out.print(outerArray[i][j] + " ");

     }
     System.out.println();

 }

edited Nov 08 '17 at 00:41

answered Nov 08 '17 at 00:34

Armin Suljovikj

60
8

This won't work unfortunately, I need row only. – Nov 08 '17 at 00:38
Okay. I posted the entire code check it out and you will see the results yourself. – Armin Suljovikj Nov 08 '17 at 00:42
Yes I have upvoted to you thanks. – Nov 08 '17 at 00:54

score 0 · Accepted Answer · answered Nov 08 '17 at 00:31

As @Pshemo mentioned, you didn't go through all your values, here is a prob way:

 for (int row = 0; row < arr.length; row++) {
        for (int column = 0; column < arr.length - 1; column++) {
            double min = arr[row][column];
            int index = column;
            for (int j = column + 1; j < arr.length; j++) {
                if (min > arr[row][j]) {
                    min = arr[row][j];
                    index = j;
                }
            }
            if (index != column) {
                arr[row][index] = arr[row][column];
                arr[row][column] = min;
            }
        }
    }

score 0 · Answer 3 · answered Nov 08 '17 at 00:34

        for (int column = 0; column < arr[row].length; column++) {
        //**insert another for loop here**
            if (arr[row][column] < minVal) {
              minVal = arr[row][column];
              index = column;
            }

        }

Your code is running once per row, and hence it is only finding the smallest and shifting to first position. You just have to make sure that the same action happens as many times as there ar items in the row. Look here for reference Bubble Sort

Sort 2D array rows

3 Answers3