Given a roman numeral, convert it to an integer.
Input is guaranteed to be within the range from 1 to 3999.
AC最快的一次。。每种字母代表一个数字。小的在左边表示右减左，小的在右边表示右加左。如IV表示4， VI表示6.
I, i: 1
V, v: 5
X, x: 10
L, l: 50
C, c: 100
D, d: 500
M, m: 1000
1 class Solution { 2 public: 3 int romanToInt(string s) { 4 int times = 1; 5 int result = 0; 6 for(int i = 0; i < s.length() - 1; i++){ 7 if(toint(s[i]) == toint(s[i+1])) times++; 8 else if(toint(s[i+1]) > toint(s[i])){ 9 result -= toint(s[i]) * times; 10 times = 1; 11 } 12 else{ 13 result += toint(s[i]) * times; 14 times = 1; 15 } 16 } 17 result += toint(s[s.length()-1]) * times; 18 return result; 19 } 20 int toint(char ch){ 21 switch(ch){ 22 case 'I': case 'i': return 1; 23 case 'V': case 'v': return 5; 24 case 'X': case 'x': return 10; 25 case 'L': case 'l': return 50; 26 case 'C': case 'c': return 100; 27 case 'D': case 'd': return 500; 28 case 'M': case 'm': return 1000; 29 } 30 } 31 };