add: 整数转罗马数字

.vscode/settings.json

@@ -1,5 +1,6 @@
 {
   "cSpell.words": [
+    "LVIII",
     "abcdefg",
     "cdefgab",
     "chuan",

src/string/integer-to-roman.js

@@ -0,0 +1,19 @@
+/**
+ * @param {number} num
+ * @return {string}
+ */
+export const intToRoman = function (num) {
+  const nums = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1]
+  const chars = ['M', 'CM', 'D', 'CD', 'C', 'XC', 'L', 'XL', 'X', 'IX', 'V', 'IV', 'I']
+  let result = ''
+  while (num) {
+    if (num >= nums[0]) { // 3 > 1 => 2 > 1 => 1 == 1
+      result += chars[0] // I => II => III
+      num -= nums[0] // 3 -> 2 => 2 -> 1 => 1 => 0
+    } else {
+      nums.shift()
+      chars.shift()
+    }
+  }
+  return result
+}

test/string/integer-to-roman.test.js

@@ -0,0 +1,9 @@
+import { intToRoman } from '../../src/string/integer-to-roman'
+
+test('整数转罗马数字', () => {
+  expect(intToRoman(2)).toBe('II')
+  expect(intToRoman(3)).toBe('III')
+  expect(intToRoman(4)).toBe('IV')
+  expect(intToRoman(9)).toBe('IX')
+  expect(intToRoman(58)).toBe('LVIII')
+})