Exercise 9: Integer to Roman Numeral
Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M. The conversion of symbol to value is given in the following chart:
| Symbol | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1000 |
A Roman numeral is formed by appending the conversions of decimal place values from highest to lowest. For example, 2 is written as II in Roman numeral -- two ones added together. 12 is written as XII, which is simply X + II. The number 27 is written as XXVII, which is XX + V + II.
Converting an integer value into a Roman numeral has the following rules:
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If the value does not start with 4 or 9, select the symbol of the maximal value that can be subtracted from the input, append that symbol to the result, subtract its value, and convert the remainder to a Roman numeral.
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If the value starts with 4 or 9 use the subtractive form representing one symbol subtracted from the following symbol, for example, 4 is 1 (I) less than 5 (V): IV and 9 is 1 (I) less than 10 (X): IX. Only the following subtractive forms are used: 4 (IV), 9 (IX), 40 (XL), 90 (XC), 400 (CD) and 900 (CM).
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Only powers of 10 (I, X, C, M) can be appended consecutively at most 3 times to represent multiples of 10. You cannot append 5 (V), 50 (L), or 500 (D) multiple times. If you need to append a symbol 4 times use the subtractive form.
Given an integer between 1 and 3999, convert it to a Roman numeral. Return a string of the Roman numeral representation.
Input: 4
Output: 'IV'
Input: 1994
Output: 'MCMXCIV'
Input: 58
Output: 'LVIII'
Sketch:
Script: