Board.groovy

boolean removePairsCandidates(Cell cell, Cell[] cells) {
    boolean theSameRecord = false
    boolean change = false
    Cell twinCell

    cells.each {
        if (it != cell && it.candidates == cell.candidates) {
            theSameRecord = true
            twinCell = it
        }
    }
    if (theSameRecord) {
        cells.findAll {
            it != cell && it != twinCell && it.candidates
        }.each { otherCell ->
            cell.candidates.each { value ->
                if (otherCell.candidates.contains(value)) {
                    otherCell.candidates -= value
                    change = true
                }
            }
        }
    }
    return change
}