Making File Names Unique — Python

# Time:  O(n)
# Space: O(n)

import collections


class Solution(object):
    def getFolderNames(self, names):
        """
        :type names: List[str]
        :rtype: List[str]
        """
        count = collections.Counter()
        result, lookup = [], set()
        for name in names:
            while True:
                name_with_suffix = "{}({})".format(name, count[name]) if count[name] else name
                count[name] += 1
                if name_with_suffix not in lookup:
                    break
            result.append(name_with_suffix)
            lookup.add(name_with_suffix)
        return result