add solution of problem 12: integer to roman

Author: ppulse

IntegerToRoman12/README.md

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+Given an integer, convert it to a roman numeral.
+
+Input is guaranteed to be within the range from 1 to 3999.

IntegerToRoman12/Solution.java

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+public class Solution {
+    public String intToRoman(int num) {
+        if (num < 1 || num > 3999)
+            return "";
+        
+        String[] map = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};
+        StringBuilder sb = new StringBuilder();
+        int[] divisor = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
+        int idx = 0;
+        int mapSize = map.length;
+        
+        while (idx < mapSize) {
+            int cnt = num / divisor[idx];
+            num %= divisor[idx];
+            
+            for (int i = 0; i < cnt; i++)
+                sb.append(map[idx]);
+            
+            idx++;
+        }
+        
+        return sb.toString();
+    }
+}