Leetcode 1647. Minimum Deletions to Make Character Frequencies Unique

class Solution:
    def minDeletions(self, s: str) -> int:
        stat = collections.defaultdict(int)
        for ch in s:
            stat[ch] += 1
        frequencies = sorted(stat.values(), reverse=True)
        count = 0
        pre = frequencies[0]
        for i in range(1, len(frequencies)):
            if pre == 1:
                count += frequencies[i]
                continue
            if frequencies[i] >= pre:
                count += frequencies[i] - pre + 1
                pre -= 1
            else:
                pre = frequencies[i]
        return count