46 lines
1.0 KiB
Markdown
46 lines
1.0 KiB
Markdown
---
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title: Integer to roman numeral
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type: snippet
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tags: [math,string]
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cover: ancient-greek-building
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dateModified: 2020-10-22T20:24:44+03:00
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---
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Converts an integer to its roman numeral representation.
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Accepts value between `1` and `3999` (both inclusive).
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- Create a lookup table containing 2-value arrays in the form of (roman value, integer).
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- Use `Array.prototype.reduce()` to loop over the values in `lookup` and repeatedly divide `num` by the value.
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- Use `String.prototype.repeat()` to add the roman numeral representation to the accumulator.
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```js
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const toRomanNumeral = num => {
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const lookup = [
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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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return lookup.reduce((acc, [k, v]) => {
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acc += k.repeat(Math.floor(num / v));
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num = num % v;
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return acc;
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}, '');
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};
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```
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```js
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toRomanNumeral(3); // 'III'
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toRomanNumeral(11); // 'XI'
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toRomanNumeral(1998); // 'MCMXCVIII'
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```
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