get max duplicate item indexes in a list using python
Question: As someone here pointed me out, for getting the max duplicated item in a list
this can be used:

    
    
    >>> from collections import Counter
    >>> mylist = [20, 20, 25, 25, 30, 30]
    >>> max(k for k,v in Counter(mylist).items() if v>1)
    30
    

but, what if i want to get the indexes instead of the values, being here `[4,
5]`

any help??

Regards...


Answer: 
    >>> from collections import defaultdict
    >>> mylist = [20, 20, 25, 25, 30, 30]
    >>> D = defaultdict(list)
    >>> for i,x in enumerate(mylist):
            D[x].append(i)
    
    
    >>> D[max(k for k,v in D.items() if len(v)>1)]
    [4, 5]
    

