Write a definition of function shuffle(s, t)
that takes two strings s and t and produces
a string that shuffles the two strings together, character
by character, starting with the first character of s,
then the first character of t, then the second character
of s, then the second character of t, etc.
When one of the strings runs out, just finish with all of
the remaining characters in the other string. For example,
shuffle("xxxx", "bbbb") = "xbxbxbxb"
shuffle("abc", "xyz") = "axbycz"
shuffle("abcdefg", "xyz") = "axbyczdefg"
shuffle("", "mouse") = "mouse"
shuffle("horse", "") = "horse"
Think about the cases that you will need. Start with easy cases.