* strings are simply arrays of chars
* how to access an item in an array
* how to write a for loop
One should be able to devise a solution to a simple problem like this without any CS course at all.
or code units/code points/grapheme clusters/emojis. Thanks to hard work of many developers string handling becomes easier over time, but I don't think it's trivial if you don't exactly specify what you mean by "string" and "character".
The human touch.