[N-0] refactor 13

Author: fishercoder1534

README.md

@@ -654,7 +654,7 @@ Your ideas/fixes/algorithms are more than welcome!
 |16|[3Sum Closest](https://leetcode.com/problems/3sum-closest/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_16.java)|O(nlogn)|O(1)|Medium|Two Pointers
 |15|[3Sum](https://leetcode.com/problems/3sum/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_15.java)|O(n^2)|O(1)|Medium|Two Pointers, Binary Search
 |14|[Longest Common Prefix](https://leetcode.com/problems/longest-common-prefix/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_14.java)| O(n*min(wordLength in this array)) | O(1) | Easy
-|13|[Roman to Integer](https://leetcode.com/problems/roman-to-integer)|[Solution](../master/src/main/java/com/fishercoder/solutions/_13.java)| O(1) | O(1) | Easy
+|13|[Roman to Integer](https://leetcode.com/problems/roman-to-integer)|[Solution](../master/src/main/java/com/fishercoder/solutions/_13.java)| O(1) | O(1) | Easy | Math, String
 |12|[Integer to Roman](https://leetcode.com/problems/integer-to-roman/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_12.java)|O(1)|O(1)|Medium| Math, String
 |11|[Container With Most Water](https://leetcode.com/problems/container-with-most-water/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_11.java)|O(n)|O(1)|Medium|
 |10|[Regular Expression Matching](https://leetcode.com/problems/regular-expression-matching/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_10.java)|O(m*n)|O(m*n)|Hard|DP

src/main/java/com/fishercoder/solutions/_13.java

@@ -12,26 +12,27 @@
 
 public class _13 {
 
-    public int romanToInt(String s) {
-        Map<Character, Integer> map = new HashMap();
-        map.put('I', 1);
-        map.put('V', 5);
-        map.put('X', 10);
-        map.put('L', 50);
-        map.put('C', 100);
-        map.put('D', 500);
-        map.put('M', 1000);
+    public static class Solution1 {
+        public int romanToInt(String s) {
+            Map<Character, Integer> map = new HashMap();
+            map.put('I', 1);
+            map.put('V', 5);
+            map.put('X', 10);
+            map.put('L', 50);
+            map.put('C', 100);
+            map.put('D', 500);
+            map.put('M', 1000);
 
-        char[] schar = s.toCharArray();
-        int result = 0;
-        for (int i = 0; i < s.length(); i++) {
-            if (i > 0 && map.get(schar[i]) > map.get(schar[i - 1])) {
-                result = result + map.get(schar[i]) - 2 * map.get(schar[i - 1]);
-            } else {
-                result = result + map.get(schar[i]);
+            int result = 0;
+            for (int i = 0; i < s.length(); i++) {
+                if (i > 0 && map.get(s.charAt(i)) > map.get(s.charAt(i - 1))) {
+                    result += map.get(s.charAt(i)) - 2 * map.get(s.charAt(i - 1));
+                } else {
+                    result += map.get(s.charAt(i));
+                }
             }
+            return result;
         }
-        return result;
     }
 
 }

src/test/java/com/fishercoder/_13Test.java

@@ -0,0 +1,31 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._13;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class _13Test {
+    private static _13.Solution1 solution1;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _13.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        assertEquals(12, solution1.romanToInt("XII"));
+    }
+
+    @Test
+    public void test2() {
+        assertEquals(1000, solution1.romanToInt("M"));
+    }
+
+    @Test
+    public void test3() {
+        assertEquals(3999, solution1.romanToInt("MMMCMXCIX"));
+    }
+}