Python計數：defaultdict和Counter

使用Python內建的defaultdict和Counter能方便的實現計數等操作

題目：3289. 數字小鎮中的搗蛋鬼

from typing import List
from collections import defaultdict, Counter

class Solution:
    def getSneakyNumbers(self, nums: List[int]) -> List[int]:
        counter = Counter(nums)
        ans = []
        for key in counter:
            if counter[key] > 1:
                ans.append(key)
        return ans
    
    def getSneakyNumbers(self, nums: List[int]) -> List[int]:
        ans = []
        d = defaultdict(int)  # 鍵不存在時呼叫int()返回0
        for i in nums:
            d[i] += 1
            if d[i] > 1:
                ans.append(i)
        return ans