Play with two Strings
Your task is to combine two strings. But consider the rule:
Input strings a and b: For every character in string a swap the casing of every occurrence of the same character in string b. Then do the same casing swap with the inputs reversed. Return a single string consisting of the changed version of a followed by the changed version of b. A char of a is in b regardless if it's in upper or lower case - see the testcases too. smile67
Longest Common Subsequence (Performance version)
Write a function lcs that accepts two strings and returns their longest common subsequence as a string. Performance matters.
JohanWiltink