12. Integer to Roman
Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.
SymbolValue I1 V5 X10 L50 C100 D500 M1000
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.
難度：medium
題目：
羅馬數字由七個符號組成：I, V, X, L, C, D 和 M.
例如，2的羅馬數為II，兩個I相挨。然而4並不是IIII.而是IV. 因為1是在5前所以由5減1構成4。同樣的規則適合9羅馬數為IX. 有6個例項需要用這種減規則：
- I 可以放置在V 和 X之前構成4和9
- X 可以放置在L 和 C之前構成40和90
- C 可以放置在D 和 M之前構成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();
}
}