共计 1895 个字符，预计需要花费 5 分钟才能阅读完成。
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: 3Output: “III”
Example 2:Input: 4Output: “IV”
Example 3:Input: 9Output: “IX”
Example 4:Input: 58Output: “LVIII”Explanation: L = 50, V = 5, III = 3.
Example 5:Input: 1994Output: “MCMXCIV”Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
难度：medium
题目：罗马数字由七个符号组成：I, V, X, L, C, D 和 M. 例如，2 的罗马数为 II，两个 I 相挨。然而 4 并不是 IIII. 而是 IV. 因为 1 是在 5 前所以由 5 减 1 构成 4。同样的规则适合 9 罗马数为 IX. 有 6 个实例需要用这种减规则：
I 可以放置在 V 和 X 之前构成 4 和 9
X 可以放置在 L 和 C 之前构成 40 和 90
C 可以放置在 D 和 M 之前构成 400 和 900
Runtime: 35 ms, faster than 96.86% of Java online submissions for Integer to Roman.
class Solution {
public String intToRoman(int num) {
StringBuilder sb = new StringBuilder();
for (; num > 0;) {
if (num – 1000 >= 0) {
sb.append(“M”);
num -= 1000;
} else if (num – 900 >= 0) {
sb.append(“CM”);
num -= 900;
} else if (num – 500 >= 0) {
sb.append(“D”);
num -= 500;
} else if (num – 400 >= 0) {
sb.append(“CD”);
num -= 400;
} else if (num – 100 >= 0) {
sb.append(“C”);
num -= 100;
} else if (num – 90 >= 0) {
sb.append(“XC”);
num -= 90;
} else if (num – 50 >= 0) {
sb.append(“L”);
num -= 50;
} else if (num – 40 >= 0) {
sb.append(“XL”);
num -= 40;
} else if (num – 10 >= 0) {
sb.append(“X”);
num -= 10;
} else if (num – 9 >= 0) {
sb.append(“IX”);
num -= 9;
} else if (num – 5 >= 0) {
sb.append(“V”);
num -= 5;
} else if (num – 4 >= 0) {
sb.append(“IV”);
num -= 4;
} else if (num – 1 >= 0) {
sb.append(“I”);
num -= 1;
}
}
return sb.toString();
}
}