add: 罗马数字转整数

README.md

@@ -76,6 +76,16 @@ LeetCode 与 LintCode 解题记录。此为个人练习仓库，代码中对重
   - LeetCode 58. 最后一个单词的长度 https://leetcode-cn.com/problems/length-of-last-word/
   - LintCode 422. 最后一个单词的长度 https://www.lintcode.com/problem/length-of-last-word/description
 
+- [整数转罗马数字](src/string/integer-to-roman.js)
+
+  - LeetCode 12. 整数转罗马数字 https://leetcode-cn.com/problems/integer-to-roman/
+  - LintCode 418. 整数转罗马数字 https://www.lintcode.com/problem/integer-to-roman/description
+
+- [罗马数字转整数](src/string/roman-to-integer.js)
+
+  - LeetCode 13. 罗马数字转整数 https://leetcode-cn.com/problems/roman-to-integer/
+  - LintCode 419. 罗马数字转整数 https://www.lintcode.com/problem/roman-to-integer/description
+
 ## 数组
 
 - [电话号码的字母组合](src/array/letter-combinations-of-a-phone-number.js)

src/string/roman-to-integer.js

@@ -0,0 +1,34 @@
+/**
+ * @param {string} s
+ * @return {number}
+ */
+export const romanToInt = function (s) {
+  const map = new Map([
+    ['I', 1],
+    ['IV', 4],
+    ['V', 5],
+    ['IX', 9],
+    ['X', 10],
+    ['XL', 40],
+    ['L', 50],
+    ['XC', 90],
+    ['C', 100],
+    ['CD', 400],
+    ['D', 500],
+    ['CM', 900],
+    ['M', 1000]
+  ])
+
+  let ans = 0
+  let i = 0
+  while (i < s.length) {
+    if (i + 1 < s.length && map.has(s.substring(i, i + 2))) {
+      ans += map.get(s.substring(i, i + 2))
+      i += 2
+    } else {
+      ans += map.get(s.substring(i, i + 1))
+      i++
+    }
+  }
+  return ans
+}

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

@@ -0,0 +1,8 @@
+import { romanToInt } from '../../src/string/roman-to-integer'
+
+test('罗马数字转整数', () => {
+  expect(romanToInt('III')).toBe(3)
+  expect(romanToInt('IV')).toBe(4)
+  expect(romanToInt('IX')).toBe(9)
+  expect(romanToInt('LVIII')).toBe(58)
+})