771. Jewles and Stones.

def numJewelsInStones(self, J: str, S: str)->int:
  freqs = {}
  count=  0

  for char in S:
    if char not in freqs:
      freqs[char] = 1
    else:
      freqs[char] += 1
    
    for char in J:
      if char in freqs:
        count += freqs[char]
  
  return count

def numJewelsInStones_defaultdict(self, J: str, S: str)->int:
  # 초기화 필요 없음
  freqs = collections.defaultdict(int)
  count = 0

  for char in S:
    freqs[char] += 1
  
  for char in J:
    count += freqs[char]
  
  return count

def numJewelsInStones_counter(self, J: str, S: str)->int:
  freqs = collections.Counter(S)
  count = 0

  for char in J:
    count += freqs[char]
  
  return count

def numJewelsInStones_one_line(self, J: str, S: str)->int:
  return sum(s in J for s in S)