Each day you put up a new word on a marquee sign with movable letters, buying just the letters you need to write it. You re-use letters you've bought for earlier words whenever possible. Given the words you want to write each day in order, output the letters you buy each day.
Example
Input: ['ONE', 'TWO', 'THREE', 'SEVENTEEN'] Output: ['ENO', 'TW', 'EHR', 'EENSV']
Day 1: You start with no letters, so to write
ONE
, you buy all its lettersE
,N
,O
.
Day 2: The next day, you want to put upTWO
(taking down theONE
). You already have anO
fromONE
, so you buy an additionalTW
.
Day 3: At this point, you haveENOWT
. To writeTHREE
, you needEHR
. Note that you need to buy a secondE
in addition to the one you have.
Day 4: To writeSEVENTEEN
, you need 4E
's total of which you already have two (not three!), so you buy two more. You also have theT
and one of theN
's, so you buy the remaining letters:EENSV
.We've output letters sorted alphabetically in this example, but you may output them in any order.
Input: A non-empty list of non-empty strings of letters A-Z
. You may use lowercase if you prefer. Lists of characters are fine for strings.
Output: Output or print the additional letters you need to buy each day. The letters for a day may be output in any order, but the days must come in the right order.
The letters from each day should be separated from other days so you can tell where a day ends. A trailing and/or leading separator is fine, both within a day or between days. Note that a day may have no letters bought, which should be reflected in the output (a space or empty line is OK, even for the last day).
Test cases
['ONE', 'TWO', 'THREE', 'SEVENTEEN']
['ENO', 'TW', 'EHR', 'EENSV']
['ONE', 'TWO', 'ONE', 'THREE']
['ENO', 'TW', '', 'EHR']
['ABC', 'AABC', 'ABBC', 'ABCC', 'AABBCC']
['ABC', 'A', 'B', 'C', '']
['SHORT', 'LOONG', 'LOOOONG', 'LOOOOOOONG', 'SHORT', 'LOOONG']
['HORST', 'GLNO', 'OO', 'OOO', '', '']
Here are all the inputs and outputs as separate lists:
[['ONE', 'TWO', 'THREE', 'SEVENTEEN'], ['ONE', 'TWO', 'ONE', 'THREE'], ['ABC', 'AABC', 'ABBC', 'ABCC', 'AABBCC'], ['SHORT', 'LOONG', 'LOOOONG', 'LOOOOOOONG', 'SHORT', 'LOOONG']]
[['ENO', 'TW', 'EHR', 'EENSV'], ['ENO', 'TW', '', 'EHR'], ['ABC', 'A', 'B', 'C', ''], ['HORST', 'GLNO', 'OO', 'OOO', '', '']]
And as space-separated strings (the trailing spaces in the outputs matter):
ONE TWO THREE SEVENTEEN
ONE TWO ONE THREE
ABC AABC ABBC ABCC AABBCC
SHORT LOONG LOOOONG LOOOOOOONG SHORT LOOONG
ENO TW EHR EENSV
ENO TW EHR
ABC A B C
HORST GLNO OO OOO
Leaderboards
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[['E', 'N', 'O'], ...]
\$\endgroup\$SHORTLONGOOOOO
valid for the last output? AKA using no delimiters? \$\endgroup\$