Given a roman numeral, convert it to an integer.
The answer is guaranteed to be within the range from 1 to 3999.
Clarification
Example
IV -> 4
XII -> 12
XXI -> 21
XCIX -> 99
LeetCode的原题，请参见我之前的博客Roman to Integer。
解法一：
class Solution { public: /** * @param s Roman representation * @return an integer */ int romanToInt(string& s) { int res = 0; unordered_map<char, int> m{{'I', 1}, {'V', 5}, {'X', 10}, {'L', 50}, {'C', 100}, {'D', 500}, {'M', 1000}}; for (int i = 0; i < s.size(); ++i) { if (i == s.size() - 1 || m[s[i]] >= m[s[i + 1]]) res += m[s[i]]; else res -= m[s[i]]; } return res; } };
解法二：
class Solution { public: /** * @param s Roman representation * @return an integer */ int romanToInt(string& s) { int res = 0; unordered_map<char, int> m{{'I', 1}, {'V', 5}, {'X', 10}, {'L', 50}, {'C', 100}, {'D', 500}, {'M', 1000}}; for (int i = 0; i < s.size(); ++i) { if (i == 0) res += m[s[i]]; else { if (m[s[i]] > m[s[i - 1]]) res += m[s[i]] - 2 * m[s[i - 1]]; else res += m[s[i]]; } } return res; } };
本文转自博客园Grandyang的博客，原文链接： 罗马数字转化成整数[LintCode] Roman to Integer，如需转载请自行联系原博主。