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116 lines
2.5 KiB
Markdown
116 lines
2.5 KiB
Markdown
---
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id: 691b559495c5cb5a37b9b483
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title: "Challenge 123: Roman Numeral Builder"
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challengeType: 29
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dashedName: challenge-123
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---
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# --description--
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Given an integer, return its equivalent value in Roman numerals.
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Roman numerals use these symbols:
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| Symbol | Value |
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| ------ | ----- |
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| I | 1 |
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| V | 5 |
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| X | 10 |
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| L | 50 |
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| C | 100 |
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| D | 500 |
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| M | 1000 |
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Roman numerals are written from largest to smallest, left to right using the following rules:
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- Addition is used when a symbol is followed by one of equal or smaller value. For example, `18` is written as `XVIII` (10 + 5 + 1 + 1 + 1 = 18).
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- Subtraction is used when a smaller symbol appears before a larger one, to represent 4 or 9 in any place value. For example, 19 is written as `XIX` (10 + (10 - 1)).
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- No symbol may be repeated more than three times in a row. Subtraction is used when you would otherwise need to write a symbol more than three times in a row. So the largest number you can write is 3999.
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Here's one more example: given `1464`, return `"MCDLXIV"` (1000 + (500 - 100) + 50 + 10 + (5 - 1)).
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# --hints--
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`to_roman(18)` should return `"XVIII"`.
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```js
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({test: () => { runPython(`
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from unittest import TestCase
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TestCase().assertEqual(to_roman(18), "XVIII")`)
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}})
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```
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`to_roman(19)` should return `"XIX"`.
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```js
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({test: () => { runPython(`
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from unittest import TestCase
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TestCase().assertEqual(to_roman(19), "XIX")`)
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}})
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```
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`to_roman(1464)` should return `"MCDLXIV"`.
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```js
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({test: () => { runPython(`
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from unittest import TestCase
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TestCase().assertEqual(to_roman(1464), "MCDLXIV")`)
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}})
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```
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`to_roman(2025)` should return `"MMXXV"`.
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```js
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({test: () => { runPython(`
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from unittest import TestCase
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TestCase().assertEqual(to_roman(2025), "MMXXV")`)
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}})
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```
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`to_roman(3999)` should return `"MMMCMXCIX"`.
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```js
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({test: () => { runPython(`
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from unittest import TestCase
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TestCase().assertEqual(to_roman(3999), "MMMCMXCIX")`)
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}})
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```
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# --seed--
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## --seed-contents--
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```py
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def to_roman(num):
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return num
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```
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# --solutions--
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```py
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def to_roman(num):
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symbols = [
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("M", 1000),
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("CM", 900),
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("D", 500),
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("CD", 400),
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("C", 100),
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("XC", 90),
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("L", 50),
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("XL", 40),
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("X", 10),
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("IX", 9),
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("V", 5),
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("IV", 4),
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("I", 1)
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]
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result = ""
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for sym, val in symbols:
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while num >= val:
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result += sym
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num -= val
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return result
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```
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