Question:

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My code:

public class Solution {
    public String intToRoman(int num) {
        if (num <= 0 || num > 3999)
            return null;
        String result = "";
        int numM = num / 1000;
        for (int i = 0; i < numM; i++)
            result += 'M';
        num = num - (num / 1000) * 1000;
        //100-999
        int numD = 0;
        int numC = 0;
        if (num >= 900) {
            num = num - 900;
            result += "CM";
        }
        else if (num >= 500){
            numD = num / 500;
            num = num - (num / 500) * 500;
            numC = num / 100;
            num = num - (num / 100) * 100;
            for (int i = 0; i < numD; i++)
                result += 'D';
            for (int i = 0; i < numC; i++)
                result += 'C';
        }
        else if (num >= 400) {
            num = num - 400;
            result += "CD";
        }
        else {
            numC = num / 100;
            num = num - (num / 100) * 100;
            for (int i = 0; i < numC; i++)
                result += 'C';
        }
        
        //10-99
        int numL = 0;
        int numX = 0;
        if (num >= 90) {
            num = num - 90;
            result += "XC";
        }
        else if (num >= 50) {
            numL = num / 50;
            num = num - (num / 50) * 50;
            numX = num / 10;
            num = num - (num / 10) * 10;
            for (int i = 0; i < numL; i++)
                result += 'L';
            for (int i = 0; i < numX; i++)
                result += 'X';
        }
        else if (num >= 40) {
            num = num - 40;
            result += "XL";
        }
        else {
            numX = num / 10;
            num = num - (num / 10) * 10;
            for (int i = 0; i < numX; i++)
                result += 'X';
        }
        
        //1-9
        int numV = 0;
        int numI = 0;
        if (num >= 9) {
            num = num - 9;
            result += "IX";
        }
        else if (num >= 5){
            numV = num / 5;
            num = num - (num / 5) * 5;
            numI = num;
            for (int i = 0; i < numV; i++)
                result += 'V';
            for (int i = 0; i < numI; i++)
                result += 'I';
        }
        else if (num >= 4) {
            num = num - 4;
            result += "IV";
        }
        else {
            numI = num;
            for (int i = 0; i < numI; i++)
                result += 'I';
        }
        
        return result;
    }
    
    public static void main(String[] args) {
        Solution test = new Solution();
        int a = 2014;
        System.out.println(test.intToRoman(a));
    }
}

My test result:

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这次题目没有什么意思。就是得先去理解下罗马数字的规则。然后写一些if语句就行。
主要的情况是，只要那么几个标识符。

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比如一个数在100-999之间。
那么就得分情况。
如果 >= 900, 那么百位上的数就可以用 CM来表示
如果 >= 500, 那就是DCCC.....
如果 >= 400, 那就是CD....
其他， 那就是CCC.....
这样之后就可以得到 两位数， XX
然后同样按照 90,50,40，其他的情况来区分。。
以此类推。。。

附带一个罗马数字表和命名准则
http://literacy.kent.edu/Minigrants/Cinci/romanchart.htm
https://en.wikipedia.org/wiki/Roman_numerals
**
总结：没多大意思。没有昨天那道水桶题那么带劲，性感！
**
Anyway, Good luck, Richardo!

My code:

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

reference:
https://discuss.leetcode.com/topic/20510/my-java-solution-easy-to-understand

直接看的答案给的最优解，记住就行。

Anyway, Good luck, Richardo! -- 09/17/2016