Integer to English Words

A payments desk prints vouchers, and each voucher carries its amount spelled out in words beside the figures. Given a non-negative integer amount, return the words the printer should put on the voucher.

The printer's vocabulary is fixed. Single figures and teens: 1 One, 2 Two, 3 Three, 4 Four, 5 Five, 6 Six, 7 Seven, 8 Eight, 9 Nine, 10 Ten, 11 Eleven, 12 Twelve, 13 Thirteen, 14 Fourteen, 15 Fifteen, 16 Sixteen, 17 Seventeen, 18 Eighteen, 19 Nineteen. Whole tens: 20 Twenty, 30 Thirty, 40 Forty, 50 Fifty, 60 Sixty, 70 Seventy, 80 Eighty, 90 Ninety. It also holds the words Hundred, Thousand, Million, Billion and Zero.

The printer works to these rules.

1. An amount of 0 prints as Zero. For every other amount the word Zero is never printed.
2. Cut the figures into groups of three digits, counting from the right, so the leftmost group may be short. Read from the left, the groups are tagged Billion, Million, Thousand, and the rightmost group carries no tag.
3. A group whose digits are all 0 prints nothing whatsoever, tag included.
4. Any other group prints, in this order: the word for its hundreds digit followed by Hundred when that digit is not 0; then the number formed by its last two digits, as one word when that number is 1 through 19, as the whole-tens word plus the units word when the units digit is not 0, as the whole-tens word by itself when the units digit is 0, and as nothing at all when both digits are 0. The group's tag comes last.
5. Exactly one space separates neighbouring words. No hyphens, no commas, no and, and no space at either end of the answer.

Examples

Constraints

• 0 <= amount <= 2^31 - 1

The signature

The editor starts with this. It matches the parent problem's shape, so a solution that works here works on a standard judge unchanged.

def spell_amount(amount: int) -> str:

public String spellAmount(int amount)