Find all the combination of substrings that add up to the given string

Question

I\'m trying to create a data structure that holds all the possible substring combinations that add up to the original string. For example, if the string is \"java\"

Answer 1

Here's one approach:

static List> substrings(String input) {

    // Base case: There's only one way to split up a single character
    // string, and that is ["x"] where x is the character.
    if (input.length() == 1)
        return Collections.singletonList(Collections.singletonList(input));

    // To hold the result
    List> result = new ArrayList<>();

    // Recurse (since you tagged the question with recursion ;)
    for (List subresult : substrings(input.substring(1))) {

        // Case: Don't split
        List l2 = new ArrayList<>(subresult);
        l2.set(0, input.charAt(0) + l2.get(0));
        result.add(l2);

        // Case: Split
        List l = new ArrayList<>(subresult);
        l.add(0, input.substring(0, 1));
        result.add(l);
    }

    return result;
}

Output:

[java]
[j, ava]
[ja, va]
[j, a, va]
[jav, a]
[j, av, a]
[ja, v, a]
[j, a, v, a]