Add to_roman_numeral

snippets/to_roman_numeral.md

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+---
+title: to_roman_numeral
+tags: math,string,intermediate
+---
+
+Converts an integer to its roman numeral representation. 
+Accepts value between `1` and `3999` (both inclusive).
+
+- Create a lookup list containing tuples in the form of (roman value, integer).
+- Use a `for` loop to iterate over the values in `lookup`, `divmod()` to update `num` with the remainder, adding the roman numeral representation to the result.
+
+```py
+def to_roman_numeral(num):
+  lookup = [
+    (1000, 'M'),
+    (900, 'CM'),
+    (500, 'D'),
+    (400, 'CD'),
+    (100, 'C'),
+    (90, 'XC'),
+    (50, 'L'),
+    (40, 'XL'),
+    (10, 'X'),
+    (9, 'IX'),
+    (5, 'V'),
+    (4, 'IV'),
+    (1, 'I'),
+  ]
+  res = ''
+  for (n, roman) in lookup:
+    (d, num) = divmod(num, n)
+    res += roman * d
+  return res
+```
+
+```py
+to_roman_numeral(3) # 'III'
+to_roman_numeral(11) # 'XI'
+to_roman_numeral(1998) # 'MCMXCVIII'
+```