Advent of Groovy code, 2017, day 1

Advent1.groovy

// http://adventofcode.com/2017/day/1

def captcha(list) {
    def last   = list[-1]
    def clean  = list.findAll { e -> 
        if (e  ==  last) { 
          last = e; true
        } else {
          last = e ; false
        } 
    }.sum()
}

captcha("1122".collect{it.toInteger()})