[Problem]
Given a roman numeral, convert it to an integer.
Input is guaranteed to be within the range from 1 to 3999.
[Analysis]
建立一个字符到数字的map之后只需要抓住两个条件：1. 输入都是有效罗马数字; 2. 当小数字在大数字左边时需要用到减法。
[Solution]
public class Solution { public int romanToInt(String s) { int result = 0; for (int i = 0; i < s.length(); i++) { int curVal = romanToDigit(s.charAt(i)); if (i + 1 < s.length()) { int nextVal = romanToDigit(s.charAt(i + 1)); if (nextVal > curVal) { result += nextVal - curVal; i++; } else { result += curVal; } } else { result += curVal; } } return result; } public int romanToDigit(char c) { switch(c) { case ‘I‘: return 1; case ‘V‘: return 5; case ‘X‘: return 10; case ‘L‘: return 50; case ‘C‘: return 100; case ‘D‘: return 500; case ‘M‘: return 1000; default: return 0; } } }
LeetCode #13 Roman to Integer (E)
原文：http://www.cnblogs.com/zhangqieyi/p/4865384.html