Make subset from varying number of arrays and array elements in JAVA

Question

I have arrays like below

A:[[1,2,3],[100,200]] 
B:[[4,5],[300,400],[500,600,700]]
C:[[6,7,8,9]]

Now I have to make sets using above array elements.My expected result should be like

Set1:[[1,2,3],[4,5],[6,7,8,9]]
Set2:[[1,2,3],[300,400],[6,7,8,9]]
Set3:[[1,2,3],[500,600,700],[6,7,8,9]]
Set4:[[100,200],[4,5],[6,7,8,9]]
Set5:[[100,200],[300,400],[6,7,8,9]]
Set6:[[100,200],[500,600,700],[6,7,8,9]]

here I want the code to be dynamic like number of array may change as well as number of elements in each array. Here I just explained with three array .

Here is the code below I have tried but it is not dynamic. the below code can solve the problem but if the number of array increases then I have to change the code manually and have to put more for loops. how can I overcome this issue?

List<Integer> setList = new ArrayList<>;
for (int j = 0; j < 4; j++) {
    for (int k = 0; k < A.length; k++) {
        for (int l = 0; l < B.length; l++) {
            for (int m = 0; m < C.length; m++) {
                List<Integer> tempList = new ArrayList<>
                tempList.add(A[k]);
                tempList.add(B[l]);
                tempList.add(C[m]);
                setList.add(tempList);

            }
        }
    }
}

You need to use recursion

Jose da Silva Gomes
– Jose da Silva Gomes

2018-03-15 06:11:00 +00:00
Commented Mar 15, 2018 at 6:11 — Jose da Silva Gomes
– Jose da Silva Gomes, Commented Mar 15, 2018 at 6:11
@JoseDaSilva how can I do that in recursion ?

kumaran ragunathan
– kumaran ragunathan

2018-03-15 06:15:17 +00:00
Commented Mar 15, 2018 at 6:15 — kumaran ragunathan
– kumaran ragunathan, Commented Mar 15, 2018 at 6:15
do you know anything about recursion?

Jose da Silva Gomes
– Jose da Silva Gomes

2018-03-15 06:43:10 +00:00
Commented Mar 15, 2018 at 6:43 — Jose da Silva Gomes
– Jose da Silva Gomes, Commented Mar 15, 2018 at 6:43

Thiyagu · Accepted Answer · 2018-03-15 08:31:49Z

You can model the original data as a 3D array

int [][][] arrays = new int[][][] {
            {{1,2,3}, {100, 200}}, //array A
            {{4,5}, {300, 400}, {500, 600, 700}},//array B
            {{6,7,8,9}} //array C
    };

If you want to add a new row (in addition to A, B, C) you just have to add a new row to that.

public static void solve(int[][][] arrays, List<List<List<Integer>>> result, List<List<Integer>> current,
                  int row) {
    if (row == arrays.length) {
        result.add(current);
        return;
    }

    for (int j = 0; j < arrays[row].length; j++) {
        List<List<Integer>> localCurrent = new ArrayList<>(current); //Copy the previous result
        List<Integer> currentData = Arrays.stream(arrays[row][j])
                .boxed()
                .collect(Collectors.toList()); //Convert current int[] to List<Integer>
        localCurrent.add(currentData);
        solve(arrays, result, localCurrent, row + 1); 
    }
}

//For int [][][] arrays mentioned eariler
List<List<List<Integer>>> result = new ArrayList<>();
List<List<Integer>> current = new ArrayList<>();

solve(arrays, result, current, 0);
for (int i = 0; i < result.size(); i++) {
    System.out.println(result.get(i));
}


[[1, 2, 3], [4, 5], [6, 7, 8, 9]]
[[1, 2, 3], [300, 400], [6, 7, 8, 9]]
[[1, 2, 3], [500, 600, 700], [6, 7, 8, 9]]
[[100, 200], [4, 5], [6, 7, 8, 9]]
[[100, 200], [300, 400], [6, 7, 8, 9]]
[[100, 200], [500, 600, 700], [6, 7, 8, 9]]

Hayk Mantashyan · Accepted Answer · 2018-03-15 06:53:03Z

0

This is what you needed :)

int[][] A = new int[][]{{1,2,3},{100,200}};
int[][] B = new int[][]{{4,5},{300,400},{500,600,700}};
int[][] C = new int[][]{{6,7,8,9}};

List<int[][]> setList = new ArrayList<>();
for (int i = 0; i < A.length; i++) {
    for (int j = 0; j < B.length; j++) {
        for (int k = 0; k < C.length; k++) {
            setList.add(new int[][]{A[i], B[j], C[k]});
        }
    }
}

edited Mar 15, 2018 at 6:53

answered Mar 15, 2018 at 6:43

Hayk Mantashyan

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