update 13

Author: fishercoder1534

Diff for: src/main/java/com/fishercoder/solutions/firstthousand/_13.java

@@ -6,6 +6,17 @@
 public class _13 {
 
     public static class Solution1 {
+        /**
+         * This is the most concise/elegant version to solve this problem:
+         * 1. use a map to hold the roman to numeric mappings;
+         * 2. we always add the number (corresponding from the char) first, then once we find that a later char has a corresponding value that is bigger than the previous char,
+         * we deduct 2 * previousCharCorrespondingValue
+         * <p>
+         * e.g. XIV step by step is computed below:
+         * 0 + 10 = 10
+         * 10 + 1 = 11
+         * 11 + (5 - 2*1) = 14
+         */
         public int romanToInt(String s) {
             Map<Character, Integer> map = new HashMap();
             map.put('I', 1);

Diff for: src/test/java/com/fishercoder/firstthousand/_13Test.java

@@ -28,4 +28,9 @@ public void test2() {
     public void test3() {
         assertEquals(3999, solution1.romanToInt("MMMCMXCIX"));
     }
+
+    @Test
+    public void test4() {
+        assertEquals(3045, solution1.romanToInt("MMMXLV"));
+    }
 }