This exercise is an interesting real-world text conversion problem involving English and Japanese characters. No advance knowledge of Japanese is required!
- Background
- Base Requirements
- Extra: Geminates
- Extra: Digraphs
- Extra: Obsoletes
- Extra Interactions
- Appendix: Conversion Table
(this is only context; you can skip this section entirely if you want)
The English alphabet has separate letters for consonant sounds (like k) and
vowel sounds (like a). The Japanese "alphabet" instead has characters called
kana that represent whole syllables (like か, which is pronounced "ka").
Kana come in two flavors, hiragana and katakana — in this exercise we'll only be
using hiragana.
To help English-speakers pronounce Japanese words without knowing kana, systems
of "romanization" were developed to express them using the English alphabet. The
result is called rōmaji (fun fact: the ji is the same one as in "emoji" —
it means "characters" or "writing"). For example, the greeting "こんにちは" can be
rendered in rōmaji as konnichiwa.
English-speakers interested in writing kana have a related problem: how do you
compose Japanese text using an English QWERTY keyboard? You can't "write rōmaji"
— it's only a pronunciation guide, so it can't be cleanly converted back into
kana. For example, the は above is actually the kana for ha, but is sometimes
pronounced wa, despite wa having its own kana. If you type w followed by
a, which character did you mean?
Wāpuro rōmaji solves this problem by providing a one-to-one mapping of
English letters to kana. For example, with a wāpuro rōmaji input system, if you
want は you must type an h followed by an a on a QWERTY keyboard. This lack
of ambiguity makes it easier for machines, and humans, to process.
At the bottom of this document you'll find a table of hiragana and their corresponding wāpuro rōmaji. This can be easily copied into your project by viewing the source of this file (the Raw button in the upper-right).
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Your program should accept valid strings of wāpuro rōmaji as input. A string is valid when it consists only of spaces and letter sequences that appear in the rōmaji column of the conversion table.
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If the input is valid, your program should output its hiragana conversion. Output should consist only of spaces and characters in the hiragana column of the conversion table.
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If the input is not valid, your program should output an error saying so (it doesn't need to explain why).
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Spaces act as word breaks in the input. Your output doesn't have to preserve the spaces, but they may change the conversion — see the examples below.
| Input | Output | Notes |
|---|---|---|
konnichiha |
こんにちは | ko+n+ni+chi+ha |
oyasuminasai |
おやすみなさい | o+ya+su+mi+na+sa+i |
yoroshiku ne |
よろしくね | preserving spaces is optional |
kana |
かな | ka+na, however... |
kan a |
かんあ | ...adding a space makes it ka+n+a |
exodia |
error | x is not a valid letter |
cheese |
error | che is not a valid syllable |
(extras can be done in any order)
Some consonants in Japanese can be "held" for an extra syllable-length (like the "k" sound in "bookkeeper"). These are called geminate consonants, and they are spelled differently from their "short" counterparts.
Geminate consonants are represented in rōmaji by doubling the first letter of a
syllable, like the pp in the word ippai. To convert these to hiragana, look
up the kana for the "short" version of the syllable (pa in this example), then
add the special character "small tsu" (っ) before it.
Some rules to be aware of:
- The first syllable of a word cannot be geminated
- Only the consonants
k,s,sh,t,ch, andpcan be geminated - Only the first letter of the consonant is doubled (
shbecomesssh)
| Input | Output | Notes |
|---|---|---|
matte |
まって | ma + (small tsu) + te |
hippu |
ひっぷ | hi + (small tsu) + pu |
kocchi |
こっち | only the first letter is doubled |
summo |
error | m is not one of the allowed consonants |
ma tte |
error | can't occur in the first syllable of a word |
(extras can be done in any order)
Our conversion table only covers the monographs of hiragana — syllables
represented by a single character. There is another category called digraphs,
which require two characters. kya, ju, and cho are examples of digraphs.
Digraphs are represented in rōmaji as:
- Consonant (must have an
ikana, cannot bew) y(except when the consonant issh,ch, orj)- Vowel (must be
a,u, oro)
To convert these to hiragana, look up the i kana for the consonant (1), then
append one of the special characters "small ya" (ゃ), "small yu" (ゅ), or
"small yo" (ょ), according to the vowel sound (3).
| Input | Output | Notes |
|---|---|---|
kya |
きゃ | ki + (small ya) |
ju |
じゅ | ji + (small yu) |
cho |
ちょ | chi + (small yo) |
wya |
error | w is not allowed in digraphs |
nye |
error | e is not one of the allowed vowels |
tya |
error | although t exists as a consonant, it has no i kana |
shyo |
error | correct spelling is sho, since the y is omitted with sh |
(extras can be done in any order)
There are two extra syllables not present in the conversion table that are
considered obsolete, and rarely seen outside of old place names or family
names: wi (ゐ) and we (ゑ).
Add an option to your program that allows and converts wi and we. When
the option is not enabled, obsolete syllables in the input should result in an
error, consistent with the base requirements.
With this option enabled, you can convert the ancient poem
Iroha: a "perfect pangram" that uses
every monographic syllable, including wi and we, exactly once.
iro ha nihoheto
chirinuru wo
wa ka yo tare so
tsune naramu
uwi no okuyama
kefu koete
asaki yume mishi
wehi mo sesu
いろはにほへと
ちりぬるを
わかよたれそ
つねならむ
うゐのおくやま
けふこえて
あさきゆめみし
ゑひもせす
Digraphs and geminate consonants may occur together. If you've implemented both of these extras, check that your program handles this situation correctly.
| Input | Output | Notes |
|---|---|---|
issho |
いっしょ |
i + (small tsu) + shi + (small yo) |
happyaku |
はっぴゃく |
ha + (small tsu) + pi + (small ya) + ku |
The obsolete syllables have no interactions, since w is already not allowed in
digraphs and cannot be geminated.
| hiragana | rōmaji |
|---|---|
| ん | n |
| あ | a |
| い | i |
| う | u |
| え | e |
| お | o |
| か | ka |
| き | ki |
| く | ku |
| け | ke |
| こ | ko |
| さ | sa |
| し | shi |
| す | su |
| せ | se |
| そ | so |
| た | ta |
| ち | chi |
| つ | tsu |
| て | te |
| と | to |
| な | na |
| に | ni |
| ぬ | nu |
| ね | ne |
| の | no |
| は | ha |
| ひ | hi |
| ふ | fu |
| へ | he |
| ほ | ho |
| ま | ma |
| み | mi |
| む | mu |
| め | me |
| も | mo |
| や | ya |
| ゆ | yu |
| よ | yo |
| ら | ra |
| り | ri |
| る | ru |
| れ | re |
| ろ | ro |
| わ | wa |
| を | wo |
| が | ga |
| ぎ | gi |
| ぐ | gu |
| げ | ge |
| ご | go |
| ざ | za |
| じ | ji |
| ず | zu |
| ぜ | ze |
| ぞ | zo |
| だ | da |
| ぢ | di |
| づ | du |
| で | de |
| ど | do |
| ば | ba |
| び | bi |
| ぶ | bu |
| べ | be |
| ぼ | bo |
| ぱ | pa |
| ぴ | pi |
| ぷ | pu |
| ぺ | pe |
| ぽ | po |
Solutions