Question

I have collection

def list = [4,1,1,1,3,5,1,1]

and I need to remove numbers which are repeated three times in a row. As a result I have to get an [4,3,5,1,1]. How to do this in groovy ?

Answer 1

This can be done by copying the list while ensuring the two previous elements are not the same as the one to be copied. If they are, drop the two previous elements, otherwise copy as normal.

This can be implemented with inject like this:

def list = [4,1,1,1,3,5,1,1]
def result = list.drop(2).inject(list.take(2)) { result, element -> 
    def prefixSize = result.size() - 2
    if ([element] * 2 == result.drop(prefixSize)) { 
        result.take(prefixSize)
    } else {
        result + element
    }
}
assert result == [4,3,5,1,1]