Question

This is the assignment: Write a method that sorts the elements of a matrix with 2 dimensions. For example

sort({{1,4}{2,3}}) 

would return a matrix

{{1,2}{3,4}}.

I dont know what im doing wrong in my code cause the output i get is 3.0, 3.0, 4.0, 4.0.

This is what i have so far any help would be appreciated.

public static void main(String[] args) {
    double[][] array =  { {1, 4}, {2, 3} };
    double[][] new_array = sort(array);
    for(int i = 0; i < array.length; i++) {
        for(int j = 0; j < array.length; j++) {
            System.out.print(new_array[i][j] + " ");
        }
    }

}

public static double[][] sort(double[][] array) {
    double[] storage = new double[array.length];
    for(int i = 0; i < array.length; i++) {
        for(int j = 0; j < array.length; j++) {
            storage[i] = array[i][j];
        }
    }
    storage = bubSort(storage);
    for(int i = 0; i < array.length; i++) {
        for(int j = 0; j < array.length; j++) {
            array[i][j] = storage[i];
        }
    }
    return array;
}

public static double[] bubSort(double[] list) {
    boolean changed = true;
    double temp;
    do {
    changed = false;
    for (int j = 0; j < list.length -1; j++)
    if (list[j] > list[j + 1]) {
        temp = list[j];
        list[j] = list[j + 1];
        list[j + 1] = temp;
        changed = true;
    }
    } while (changed);
    return list;
}

}

Answer 1

The main problem that you are experiencing is how you are copying the values from the 2d array into the 1d array. You are actually only copy two values into an array of length 2. The length of a 2d array is not the full m x n length.

I will give a small hint how you can go about copying from the 2d array into the 1d array, but it is up to you to figure out how to copy back from the 1d array into the 2d array. Also, how would you go about finding the full length of the array?

    double[] storage = new double[4];//You should calculate this value
    int k = 0;
    for (int i = 0; i < array.length; i++) {
        for (int j = 0; j < array.length; j++) {
            storage[k++] = array[i][j];
        }
    }

Your bubble sort works fine, but then you are copying the values back wrong. Try printing the array storage after the sort and you will see that it is now correct.