How to find repeating sequence of Integers in an array of Integers?

Question

How to find repeating sequence of Integers in an array of Integers?

00 would be repeating, so would 123123, but 01234593623 would not be.

I have an idea to h

Answer 1

@MiljenMikic answer's is great, especially since the grammar isn't actually regular. :D

If you want to do it on an array in general, or want to understand it, this does pretty much exactly what the regex does:

public static void main(String[] args) {
    int[] arr = {0, 1, 2, 3, 2, 3}; // 2, 3 repeats at position 2.

    // for every position in the array:
    for (int startPos = 0; startPos < arr.length; startPos++) {
        // check if there is a repeating sequence here:

        // check every sequence length which is lower or equal to half the
        // remaining array length: (this is important, otherwise we'll go out of bounds)
        for (int sequenceLength = 1; sequenceLength <= (arr.length - startPos) / 2; sequenceLength++) {

            // check if the sequences of length sequenceLength which start
            // at startPos and (startPos + sequenceLength (the one
            // immediately following it)) are equal:
            boolean sequencesAreEqual = true;
            for (int i = 0; i < sequenceLength; i++) {
                if (arr[startPos + i] != arr[startPos + sequenceLength + i]) {
                    sequencesAreEqual = false;
                    break;
                }
            }
            if (sequencesAreEqual) {
                System.out.println("Found repeating sequence at pos " + startPos);
            }
        }
    }
}