public boolean getToZero(List<Integer> arr, int startingIdx) {
    int currentVal = arr.get(startingIdx);
    if(currentVal==0){
        return true;
    } else if (currentVal == null){
        return false;
    } else {
        arr.set(startingIdx, null);
        int topVal = startingIdx + arr.get(startingIdx);
        int bottomVal = startingIdx - arr.get(startingIdx);
        if (bottomVal >= 0) {
            boolean foundOnBottom = getToZero(arr, bottomVal);
        }
        if (topVal <= arr.size()){
            boolean foundOnTop = getToZero(arr, topVal);
        }

        return foundOnBottom==true || foundOnTop == true;
    }

}