Count the number of Duplicates
Count the number of Duplicates Write a function that will return the count of distinct case-insensitive alphabetic characters and numeric digits that occur more than once in the input string.The input string can be assumed to contain only alphanumeric characters, including digits, uppercase and lowercase alphabets. Example "abcde" -> 0 # no characters repeats more than once "aabbcde" -> 2 # 'a' and 'b' "aabbcdeB" -> 2 # 'a' and 'b' "indivisibility" -> 1 # 'i' "Indivisibilities" -> 2 # 'i' and 's' "aa11" -> 2 # 'a' and '1' 解题思路 函数功能：计算字符串中重复的字符有多少个。我们只要先判断字符是否重复，然后再计算有多少个字符重复。 ...