C++ Solution: int pickingNumbers(vector a) {

sort(a.begin(), a.end());

int start = 0;
int stop = 1;
int res = 0;

while(stop < a.size()) 
{
    if(abs(a[start] - a[stop]) <= 1)
    {
        stop++;
    }
    else
    {
        res = max(res, stop - start);
        start = stop;
        stop++;
    }
}

res = max(res, stop - start);

return res;

}