CODEWITHSUNDEEP
javaarraysrecursion
John Wesley Hostetter
John Wesley Hostetter

Reputation: 63

Finding the possible combinations of a two dimensional array

I'm stuck on the following problem using Java. I will include my code at the bottom of this post. I get most of the combinations however I can't figure out a way to get my column variable to be 0 for the remainder of my recursive calls which would help me in getting all combinations. The solution must work for two dimensional arrays of all sizes. Preferably I would like the solution to be entirely recursion - no loops. Thank you for any insight you may provide.

Given the definition of a 2D array such as follows:

String[][] data = {
 {"A", "B"},
 {"1", "2"},
 {"XX","YY","ZZ"}
};

Write a recursive program that outputs all combinations of each subarray in order. In the previous example, the desired output might look like the following:

A 1 XX
A 1 YY
A 1 ZZ
A 2 XX
A 2 YY
A 2 ZZ
B 1 XX
B 1 YY
B 1 ZZ
B 2 XX
B 2 YY
B 2 ZZ

Your program should work with arbitrarily sized arrays in either dimension. For instance, consider the following input array:

String[][] data = {
 {"A"},
 {"1"},
 {"2"},
 {"XX","YY"}
};

Should output:

A 1 2 YY
A 1 2 YY

My solution so far:

private String[][] data = {
        {"A", "B"},
        {"1", "2"},
        {"XX","YY","ZZ"}
};

public void combinations() {
    helperMethod("",0, 0);
}

private void helperMethod(String oldCombination, int row, int col) {
    String newCombination = oldCombination + data[row][col];

    if (row == data.length - 1) {
        System.out.println(newCombination);
    }

    if (row < data.length - 1) {
        helperMethod(newCombination, row + 1, col);
    }

    if (col < data[row].length - 1) {
        helperMethod(oldCombination, row, col + 1);
    }
}

Upvotes: 3

Views: 2426

Answers (1)

Bubletan
Bubletan

Reputation: 3863

When you move to the next row, you have to reset the column back to zero:

if (row < data.length - 1) {
    helperMethod(newCombination, row + 1, 0); // 0 instead of col
}

With that small change it seems to work correctly at least with the test cases you provided.

Upvotes: 2

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