minimum_char.py

# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
import collections
def solution(S):
    # write your code in Python 3.6
    # create an empty dictionary to store the values of S
    f_dict = collections.defaultdict(int)
    # loop S
    for i in S:
        # increase number of times each character exists in S
        f_dict[i] += 1
    # create an empty list to store the values in f_dict 
    f_list = []
    
    for key, value in f_dict.items():
        f_list.append(value)

    f_list.sort(reverse=True)

    f_set = set()

    count = 0
    for v in f_list:
        if v in f_set:
            while True:
                v -= 1
                count += 1
                if v not in f_set:
                    break

        if v != 0:
            f_set.add(v)

    return count