1. 題目描述：

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

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

• 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.

2. 思路分析：

題目的意思是將普通int轉成羅馬數字，並給出了羅馬數字的表示方式。

其中每兩個階段的之間有一個減法的表示，比如900=CM， C寫在M前面表示M-C。

題目的範圍給到3999，感覺情況不多直接打表其實更快。

3. Java程式碼：

程式碼：

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