定义数组arr，值为[‘a’, ‘b’, ‘b’, ‘c’, ‘d’, ’d’]，统计重复的字符有多少个，几种方法

有以下几种方法可以统计重复的字符数量:

1. 使用Counter类

from collections import Counter

arr = ['a', 'b', 'b', 'c', 'd', 'd']
counter = Counter(arr)

# 统计重复的字符数量
duplicate_count = sum([count - 1 for count in counter.values() if count > 1])
print(duplicate_count) # 3

# 统计重复的字符种类数量
duplicate_type_count = len([count for count in counter.values() if count > 1])
print(duplicate_type_count) # 2

2. 使用set和count方法

arr = ['a', 'b', 'b', 'c', 'd', 'd']
duplicate_count = sum([arr.count(x) - 1 for x in set(arr) if arr.count(x) > 1])
print(duplicate_count) # 3

duplicate_type_count = len([x for x in set(arr) if arr.count(x) > 1])
print(duplicate_type_count) # 2

3. 使用for循环和字典

arr = ['a', 'b', 'b', 'c', 'd', 'd']
count_dict = {}

# 统计每个字符出现的次数
for char in arr:
    if char not in count_dict:
        count_dict[char] = 0
    count_dict[char] += 1

# 统计重复的字符数量
duplicate_count = sum([count - 1 for count in count_dict.values() if count > 1])
print(duplicate_count) # 3

# 统计重复的字符种类数量
duplicate_type_count = len([count for count in count_dict.values() if count > 1])
print(duplicate_type_count) # 2