# Kata question
In an even word, each letter occurs an even number of times.
Write a function solution that, given a string S consisting of N characters, returns the minimum number of letters that must be deleted to obtain an even word.
Examples:
1. Given S = "acbcbba", the function should return 1 (one letter b must be deleted).
2. Given S = "axxaxa", your function should return 2 (one letter a and one letter x must be deleted).
You are given a non-empty string S consisting of N characters.
In this problem we consider only strings that consist of lower-case English letters (a−z) and spaces.
S can be divided into words by splitting it at the spaces and removing them. We want to reverse every word in S. For example, given S = "we test coders", there are three words: "we", "test" and "coders". Reversing the words gives "ew", "tset" and "sredoc".
The goal is to return a string with every word in string S reversed and separated by spaces, so the result in the above example should be "ew tset sredoc".
You can assume that if there are K spaces in S then there are exactly K + 1 words.
Write a function: def solution(S) that, given a non-empty string S consisting of N characters, returns the reversal of every word of S.
For example, given S = "we test coders", the function should return "ew tset sredoc", as explained above.
Write an efficient algorithm for the following assumptions: the length of string S is within the range [1..200,000]; string S consists only of lower-case letters (a−z) and spaces.
Task idea contributed by Stephen Law of Electrum. 3. Given S = "aaaa", your function should return 0 (there is no need to delete any letters).
Write an efficient algorithm for the following assumptions:
N is an integer within the range [0..200,000];
string S is made only of lowercase letters (a−z).