Filling a 2d array with numbers in a rhombus form

Question

I need some help filling a 2D array using a nested for loop. The desired output is this...

20.0 19.0 18.0 17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0
19.0 18.0 17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0
18.0 17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0
17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0
16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0
15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 6.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0
14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0
13.0 12.0 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0
12.0 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0
11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0
10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0
12.0 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0
13.0 12.0 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0
14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0
15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 6.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0
16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0
17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0
18.0 17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0
19.0 18.0 17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0
20.0 19.0 18.0 17.0 16.0 15.0 14.0 13.0 12.0 11.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0

This is my code to fill the array...

int row;
int column;
int counter = 10;
int counter1 = 10;
for (row = 0; row < array.length; row++) {
    array[row][0] = obj.getZ(10, counter);
    counter--;
    for (column = 0; column < array[row].length; column++) {
        array[row][column] = obj.getZ(counter1, 10);
        counter1--;

I already declared the array to be 20 by 20 and obj.getZ is just simply calling this method...

public double getZ(double x, double y) {
    double z = (Math.abs(x) + Math.abs(y));
    return z;

The array is the z value which is formed by the absolute values of x and y.

score 2 · Accepted Answer · edited Jan 14 '21 at 23:58

Not the best solution, but it should solve the issue:

import java.util.Arrays;

class Scratch {
    public static void main(String[] args) {
        int[][] arr = new int[21][21];
        int row = 20;
        int column = 0;
        for (int i = 0; i < 21; i++) {
            column = row;
            for (int j = 0; j < 21; j++) {
                arr[i][j] = column;
                if (j < 10) {
                    column = column - 1;
                } else {
                    column = column + 1;
                }
            }
            if (i < 10) {
                row = row - 1;
            } else {
                row = row + 1;
            }
        }
        for (int[] arrRow : arr) {
            System.out.println(Arrays.toString(arrRow));
        }
    }
}

And result is:

[20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
[19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
[18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18]
[17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17]
[16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]
[15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
[14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]
[13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]
[12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
[11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
[10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
[11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
[12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
[13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]
[14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]
[15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
[16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]
[17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17]
[18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18]
[19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]
[20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]

score 0 · Answer 2 · 2021-02-18T12:24:13.970

You can create and fill this array using IntStream as follows:

int m = 10;
int n = 10;
int[][] arr = IntStream.rangeClosed(-m, m)
        .mapToObj(i -> IntStream.rangeClosed(-n, n)
                .map(j -> Math.abs(i) + Math.abs(j))
                .toArray())
        .toArray(int[][]::new);

// output
Arrays.stream(arr).map(row -> Arrays.stream(row)
        .mapToObj(String::valueOf)
        .collect(Collectors.joining(" ")))
        .forEach(System.out::println);

20 19 18 17 16 15 14 13 12 11 10 11 12 13 14 15 16 17 18 19 20
19 18 17 16 15 14 13 12 11 10 9 10 11 12 13 14 15 16 17 18 19
18 17 16 15 14 13 12 11 10 9 8 9 10 11 12 13 14 15 16 17 18
17 16 15 14 13 12 11 10 9 8 7 8 9 10 11 12 13 14 15 16 17
16 15 14 13 12 11 10 9 8 7 6 7 8 9 10 11 12 13 14 15 16
15 14 13 12 11 10 9 8 7 6 5 6 7 8 9 10 11 12 13 14 15
14 13 12 11 10 9 8 7 6 5 4 5 6 7 8 9 10 11 12 13 14
13 12 11 10 9 8 7 6 5 4 3 4 5 6 7 8 9 10 11 12 13
12 11 10 9 8 7 6 5 4 3 2 3 4 5 6 7 8 9 10 11 12
11 10 9 8 7 6 5 4 3 2 1 2 3 4 5 6 7 8 9 10 11
10 9 8 7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9 10
11 10 9 8 7 6 5 4 3 2 1 2 3 4 5 6 7 8 9 10 11
12 11 10 9 8 7 6 5 4 3 2 3 4 5 6 7 8 9 10 11 12
13 12 11 10 9 8 7 6 5 4 3 4 5 6 7 8 9 10 11 12 13
14 13 12 11 10 9 8 7 6 5 4 5 6 7 8 9 10 11 12 13 14
15 14 13 12 11 10 9 8 7 6 5 6 7 8 9 10 11 12 13 14 15
16 15 14 13 12 11 10 9 8 7 6 7 8 9 10 11 12 13 14 15 16
17 16 15 14 13 12 11 10 9 8 7 8 9 10 11 12 13 14 15 16 17
18 17 16 15 14 13 12 11 10 9 8 9 10 11 12 13 14 15 16 17 18
19 18 17 16 15 14 13 12 11 10 9 10 11 12 13 14 15 16 17 18 19
20 19 18 17 16 15 14 13 12 11 10 11 12 13 14 15 16 17 18 19 20

For double[][] array it works the same:

int m = 10;
int n = 10;
double[][] arr = IntStream.rangeClosed(-m, m)
        .mapToObj(i -> IntStream.rangeClosed(-n, n)
                .mapToDouble(j -> Math.abs(i) + Math.abs(j))
                .toArray())
        .toArray(double[][]::new);

// formatted output
Arrays.stream(arr).map(row -> Arrays.stream(row)
        .mapToObj(i -> String.format("%4.1f", i))
        .collect(Collectors.joining(" ")))
        .forEach(System.out::println);

20,0 19,0 18,0 17,0 16,0 15,0 14,0 13,0 12,0 11,0 10,0 11,0 12,0 13,0 14,0 15,0 16,0 17,0 18,0 19,0 20,0
19,0 18,0 17,0 16,0 15,0 14,0 13,0 12,0 11,0 10,0  9,0 10,0 11,0 12,0 13,0 14,0 15,0 16,0 17,0 18,0 19,0
18,0 17,0 16,0 15,0 14,0 13,0 12,0 11,0 10,0  9,0  8,0  9,0 10,0 11,0 12,0 13,0 14,0 15,0 16,0 17,0 18,0
17,0 16,0 15,0 14,0 13,0 12,0 11,0 10,0  9,0  8,0  7,0  8,0  9,0 10,0 11,0 12,0 13,0 14,0 15,0 16,0 17,0
16,0 15,0 14,0 13,0 12,0 11,0 10,0  9,0  8,0  7,0  6,0  7,0  8,0  9,0 10,0 11,0 12,0 13,0 14,0 15,0 16,0
15,0 14,0 13,0 12,0 11,0 10,0  9,0  8,0  7,0  6,0  5,0  6,0  7,0  8,0  9,0 10,0 11,0 12,0 13,0 14,0 15,0
14,0 13,0 12,0 11,0 10,0  9,0  8,0  7,0  6,0  5,0  4,0  5,0  6,0  7,0  8,0  9,0 10,0 11,0 12,0 13,0 14,0
13,0 12,0 11,0 10,0  9,0  8,0  7,0  6,0  5,0  4,0  3,0  4,0  5,0  6,0  7,0  8,0  9,0 10,0 11,0 12,0 13,0
12,0 11,0 10,0  9,0  8,0  7,0  6,0  5,0  4,0  3,0  2,0  3,0  4,0  5,0  6,0  7,0  8,0  9,0 10,0 11,0 12,0
11,0 10,0  9,0  8,0  7,0  6,0  5,0  4,0  3,0  2,0  1,0  2,0  3,0  4,0  5,0  6,0  7,0  8,0  9,0 10,0 11,0
10,0  9,0  8,0  7,0  6,0  5,0  4,0  3,0  2,0  1,0  0,0  1,0  2,0  3,0  4,0  5,0  6,0  7,0  8,0  9,0 10,0
11,0 10,0  9,0  8,0  7,0  6,0  5,0  4,0  3,0  2,0  1,0  2,0  3,0  4,0  5,0  6,0  7,0  8,0  9,0 10,0 11,0
12,0 11,0 10,0  9,0  8,0  7,0  6,0  5,0  4,0  3,0  2,0  3,0  4,0  5,0  6,0  7,0  8,0  9,0 10,0 11,0 12,0
13,0 12,0 11,0 10,0  9,0  8,0  7,0  6,0  5,0  4,0  3,0  4,0  5,0  6,0  7,0  8,0  9,0 10,0 11,0 12,0 13,0
14,0 13,0 12,0 11,0 10,0  9,0  8,0  7,0  6,0  5,0  4,0  5,0  6,0  7,0  8,0  9,0 10,0 11,0 12,0 13,0 14,0
15,0 14,0 13,0 12,0 11,0 10,0  9,0  8,0  7,0  6,0  5,0  6,0  7,0  8,0  9,0 10,0 11,0 12,0 13,0 14,0 15,0
16,0 15,0 14,0 13,0 12,0 11,0 10,0  9,0  8,0  7,0  6,0  7,0  8,0  9,0 10,0 11,0 12,0 13,0 14,0 15,0 16,0
17,0 16,0 15,0 14,0 13,0 12,0 11,0 10,0  9,0  8,0  7,0  8,0  9,0 10,0 11,0 12,0 13,0 14,0 15,0 16,0 17,0
18,0 17,0 16,0 15,0 14,0 13,0 12,0 11,0 10,0  9,0  8,0  9,0 10,0 11,0 12,0 13,0 14,0 15,0 16,0 17,0 18,0
19,0 18,0 17,0 16,0 15,0 14,0 13,0 12,0 11,0 10,0  9,0 10,0 11,0 12,0 13,0 14,0 15,0 16,0 17,0 18,0 19,0
20,0 19,0 18,0 17,0 16,0 15,0 14,0 13,0 12,0 11,0 10,0 11,0 12,0 13,0 14,0 15,0 16,0 17,0 18,0 19,0 20,0

^{See also: How to print a given diamond pattern?}

Filling a 2d array with numbers in a rhombus form

2 Answers2

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