Sorting 2D array of integers by column

Question

I need to build a method in Java where the input is a 2D array of integers and get as a result a 2D array of integers where each element makes reference to a position of an element in a column. Let me explain that with an example. Consider as an input for the method a 2D arrays of 5x5 as follow:

int[][] array = new int[][]{
        {124, 188, 24, 254, 339},
        {0, 7, 77, 145, 159},
        {206, 340, 280, 523, 433},
        {310, 265, 151, 411, 398},
        {24, 104, 0, 183, 198}};

Now I need to build a new 2D array of integer (I will call newArray in the following) according to:

• The minimum value of column 0 in the array is 0 and is associated with row 1 (then, I need to assign a 1 in newArray[0][0]).

• Next, the minimum value of column 0 in the array is 24 and is associated with row 4 (then, I need to assign a 4 in newArray[1][0]).

• Then, the minimum value of column 0 in the array is 124 and is associated with row 0 (then, I need to assign a 0 in newArray[2][0]).

• And so on for each column...

The final output of the method must be something like the following 2d array.

Any help would be highly appreciated.

Answer 1

If I understood correctly :

IN :
     {{124, 188, 24,  254, 339},
      {0,   7,   77,  145, 159},
      {206, 340, 280, 523, 433},
      {310, 265, 151, 411, 398},
      {24,  104, 0,   183, 198}}

OUT :
     {{1, 1, 4, 1, 1}
      {4, 4, 0, 4, 4}
      {0, 0, 1, 0, 0}
      {2, 3, 3, 3, 3}
      {3, 2, 2, 2, 2}

Here's the code :

public static int[][] createArray(int[][] a) {
    int[][] nA = new int[a.length][a[0].length];
    int[] col = new int[a.length];
    int minIndex = -1;
    for (int i = 0; i < a.length; i++) {
        // First get the col out
        for (int j = 0; j < a[0].length; j++) {
            col[j] = a[j][i];
        }
        // Loop through the col
        for (int k = 0; k < a[0].length; k++) {
            int min = Integer.MAX_VALUE;
            // Loop through the remaining numbers of the col
            for (int j = 0; j < col.length; j++) {
                // Find the remaining lowest number
                if (min > col[j]) {
                    min = col[j];
                    minIndex = j;
                }
            }
            // Delete the number from the array
            col[minIndex] = Integer.MAX_VALUE;
            // Set this number in the final array
            nA[k][i] = minIndex;
        }
    }
    return nA;
}

There might be an easier way, but it works !