@@ -55,11 +55,11 @@
 | [Graph](https://.com/fluency03/leetcode-java/blob/master/src/graph) |
 
 
-# Total: 527
+# Total: 530
 
 | Easy | Medium | Hard | - |
 |:-------:|:-------:|:----:|:---:|
-| 141 | 285 | 89 | 11 |
+| 141 | 287 | 90 | 12 |
 
 
 | Question | Solution | Difficulty |
@@ -73,6 +73,7 @@
 | [8. String to Integer (atoi)](https://leetcode.com/problems/string-to-integer-atoi/) | [Solution](https://.com/fluency03/leetcode-java/blob/master/src/StringToInteger8.java) | Medium |
 | [10. Regular Expression Matching](https://leetcode.com/problems/regular-expression-matching/) | [Solution](https://.com/fluency03/leetcode-java/blob/master/src/RegularExpressionMatching10.java) | Hard |
 | [11. Container With Most Water](https://leetcode.com/problems/container-with-most-water/) | [Solution](https://.com/fluency03/leetcode-java/blob/master/src/ContainerWithMostWater11.java) | Medium |
+| [12. Integer to Roman](https://leetcode.com/problems/integer-to-roman/) | [Solution](https://.com/fluency03/leetcode-java/blob/master/src/IntegerToRoman12.java) | Medium |
 | [13. Roman to Integer](https://leetcode.com/problems/roman-to-integer/) | [Solution](https://.com/fluency03/leetcode-java/blob/master/src/RomanToInteger13.java) | Easy |
 | [14. Longest Common Prefix](https://leetcode.com/problems/longest-common-prefix/) | [Solution](https://.com/fluency03/leetcode-java/blob/master/src/LongestCommonPrefix14.java) | Easy |
 | [15. 3Sum](https://leetcode.com/problems/3sum/) | [Solution](https://.com/fluency03/leetcode-java/blob/master/src/ThreeSum15.java) | Medium |

@@ -0,0 +1,103 @@
+/**
+* Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.
+*
+* Symbol Value
+* I 1
+* V 5
+* X 10
+* L 50
+* C 100
+* D 500
+* M 1000
+*
+* For example, two is written as II in Roman numeral, just two one's added
+* together. Twelve is written as, XII, which is simply X + II. The number
+* twenty seven is written as XXVII, which is XX + V + II.
+*
+* Roman numerals are usually written largest to smallest from left to right.
+* However, the numeral for four is not IIII. Instead, the number four is
+* written as IV. Because the one is before the five we subtract it making
+* four. The same principle applies to the number nine, which is written as IX.
+*
+* There are six instances where subtraction is used:
+*
+* I can be placed before V (5) and X (10) to make 4 and 9.
+* X can be placed before L (50) and C (100) to make 40 and 90.
+* C can be placed before D (500) and M (1000) to make 400 and 900.
+*
+* Given an integer, convert it to a roman numeral. Input is guaranteed to be
+* within the range from 1 to 3999.
+*
+* Example 1:
+* Input: 3
+* Output: "III"
+*
+* Example 2:
+* Input: 4
+* Output: "IV"
+*
+* Example 3:
+* Input: 9
+* Output: "IX"
+*
+* Example 4:
+* Input: 58
+* Output: "LVIII"
+* Explanation: L = 50, V = 5, III = 3.
+*
+* Example 5:
+* Input: 1994
+* Output: "MCMXCIV"
+* Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
+*/
+
+public class IntegerToRoman12 {
+// 1, 5, 10, 50, 100, 500, 1000
+private static char[] R = new char[]{'I', 'V', 'X', 'L', 'C', 'D', 'M'};
+public String intToRoman(int num) {
+StringBuilder sb = new StringBuilder();
+int base = 0;
+while (num > 0) {
+int digit = num % 10;
+if (digit > 0) {
+char[] cur = curr(digit, base);
+sb.insert(0, cur);
+}
+num /= 10;
+base += 2;
+}
+return sb.toString();
+}
+
+private char[] curr(int digit, int base) {
+if (digit >= 1 && digit <= 3) {
+char[] res = new char[digit];
+Arrays.fill(res, R[base]);
+return res;
+} else if (digit == 4) {
+return new char[]{R[base], R[base+1]};
+} else if (digit == 5) {
+return new char[]{R[base+1]};
+} else if (digit >= 6 && digit <= 8) {
+char[] res = new char[digit-5+1];
+Arrays.fill(res, R[base]);
+res[0] = R[base+1];
+return res;
+} else { // 9
+return new char[]{R[base], R[base+2]};
+}
+}
+
+
+/**
+* https://leetcode.com/problems/integer-to-roman/discuss/6274/Simple-Solution
+*/
+public static String intToRoman2(int num) {
+String M[] = {"", "M", "MM", "MMM"};
+String C[] = {"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"};
+String X[] = {"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"};
+String I[] = {"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"};
+return M[num/1000] + C[(num%1000)/100] + X[(num%100)/10] + I[num%10];
+}
+
+}