Integer to English Words

Spelling an integer in words turns a number like 1234567 into the phrase you would say out loud — One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven. You implement integerToEnglishWords(n), which takes a non-negative integer and returns its English name as capitalized words separated by single spaces. This is the LeetCode 273 problem, and the naming follows standard English numerals.

The catch is place value. English does not name digits one at a time — it groups them in threes (thousands, millions, billions), names each group of three, and glues on a scale word. Along the way it has special one-word names for the teens (Thirteen, not Ten Three) and joins tens and ones without a hyphen (Twenty One).

Signature

integerToEnglishWords(n: number): string
// n is an integer, 0 <= n <= 2_147_483_647

Examples

integerToEnglishWords(0);    // 'Zero'
integerToEnglishWords(21);   // 'Twenty One'
integerToEnglishWords(105);  // 'One Hundred Five'
integerToEnglishWords(1000); // 'One Thousand'

integerToEnglishWords(1234567);
// 'One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven'

integerToEnglishWords(1000005);
// 'One Million Five'   (the empty thousands group adds nothing)

Notes

• Range — n is a non-negative integer up to 2147483647. That reaches the billions, so the scale words you need are Thousand, Million, and Billion.
• Zero — integerToEnglishWords(0) returns 'Zero'. Zero is the only input where the word Zero appears; it never shows up inside a larger number.
• No hyphens, no "and" — write Twenty One, not Twenty-One; write One Hundred Five, not One Hundred and Five. Every word is capitalized and separated by exactly one space.
• Spacing — the result has no leading space, no trailing space, and no double spaces, even when a middle group of digits is all zeros (1000005 is One Million Five, with no gap where the thousands would go).
• Teens are special — 13 is Thirteen, not Ten Three; the numbers 11 through 19 each have their own name.
• What you can assume — n is always a valid non-negative integer. You do not need to handle negative numbers, decimals, or strings.