12. Integer to Roman - Medium
阿新 • • 發佈:2018-12-20
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
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
IX
. There are six instances where subtraction is used:
I
can be placed beforeV
(5) andX
(10) to make 4 and 9.X
can be placed beforeL
C
(100) to make 40 and 90.C
can be placed beforeD
(500) andM
(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.
reference: grandyang三種解法
time: O(n), space: O(1)
class Solution { public String intToRoman(int num) { char[] roman = {'M', 'D', 'C', 'L', 'X', 'V', 'I'}; int[] value = {1000, 500, 100, 50, 10, 5, 1}; StringBuilder sb = new StringBuilder(); for(int i = 0; i <= 6; i += 2) { int n = num / value[i]; if(n < 4) { for(int j = 0; j < n; j++) sb.append(roman[i]); } else if(n == 4) { sb.append(roman[i]); sb.append(roman[i-1]); } else if(n > 4 && n < 9) { sb.append(roman[i-1]); for(int j = 0; j < n - 5; j++) sb.append(roman[i]); } else { sb.append(roman[i]); sb.append(roman[i-2]); } num %= value[i]; } return sb.toString(); } }