String Problems

0:06 even characters Write a function that returns a sequence (index begins with 1) of all the even characters from a string. If the string is smaller than two characters or longer than 100 characters, the function should return "invalid string". 3:17 characters not common You are given two strings a and b and your task will be to return the characters that are not common in the two strings. 6:36 reverse words Complete the solution so that it reverses all of the words within the string passed in. 9:18 count vowels Return the number (count) of vowels in the given string. We will consider a, e, i, o, u as vowels for this program (but not y). The input string will only consist of lower-case letters and/or spaces.