[LeetCode] 13. Roman to Integer

题目

13. Roman to Integer

描述

把用字符串形式表达的罗马数字转换成十进制整数形式，整数范围为 1 到 3999。

代码

class Solution {
public:
	int romanToInt(string s){
		map<char, int> roman;
		roman['I'] = 1;
		roman['V'] = 5;
		roman['X'] = 10;
		roman['L'] = 50;
		roman['C'] = 100;
		roman['D'] = 500;
		roman['M'] = 1000;

		int sum = 0;
		int len = s.size();
		for(int i=0; i<len;){
			int c1 = s[i];
			if(i==len-1){ // last char
				sum += roman[s[i]];
				break;
			}
			else{
				int n=i+1;
				while(s[n]==s[i] && n<len)
					n++;
				n = n - (i+1)+1;
				if(n>1){
					sum += n*roman[s[i]];
					i += n;
				}
				else{
					if(roman[s[i]] < roman[s[i+1]]){
						sum += roman[s[i+1]] - roman[s[i]];
						i+=2;
					}
					else{
						sum += roman[s[i]];
						i++;
					}
				}
			}
		}
		return sum;
	}
};