Combining two strings together (not concatenation)

[ichabod801]

Then I think you are really over complicating this. When the second string has a 3, the combined string should have a 3. Otherwise the combined string should have what the first string has.

So loop through the indexes. If the second string's character at that index is '3', add '3' to the combined string. Otherwise take whatever is at that index in the current string, and add that to the combined string.

Really, it would be better to do this by zipping together the two strings, but I'm trying to keep it basic.