Roman numerals are represented by seven different
symbols:I,V,X,L,C,DandM.Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1000For example, two is written as
IIin Roman numeral, just two one’s added together.
Twelve is written as,XII, which is simplyX+II. The number twenty seven is written asXXVII, which isXX+V+II.Roman numerals are usually written largest to smallest
from left to right. However, the numeral for four is
notIIII. Instead, the number four is written asIV. Because the one is before the five we subtract it
making four. The same principle applies to the number
nine, which is written asIX. There are six instances where subtraction is used:
Ican be placed beforeV(5) andX(10) to make 4 and 9.Xcan be placed beforeL(50) andC(100) to make 40 and 90.Ccan be placed beforeD(500) andM(1000) to make 400 and 900.Given a roman numeral, convert it to an integer. Input
is guaranteed to be within the range from 1 to 3999.
/**
* @param {string} s
* @return {number}
*/
var romanToInt = function(s) {
var d = s.split("");
var result = 0, prev = '';
var roman = {
'I': 1,
'V': 5,
'X': 10,
'L': 50,
'C': 100,
'D': 500,
'M': 1000,
};
for(var i of d){
if(i == 'M'){
result = (prev == 'C') ? result-roman[prev]+900 : result + 1000;
} else if(i == 'D'){
result = (prev == 'C') ? result-roman[prev]+400 : result + 500;
} else if(i == 'C'){
result = (prev == 'X') ? result-roman[prev]+90 : result + 100;
} else if(i == 'L'){
result = (prev == 'X') ? result-roman[prev]+40 : result + 50;
} else if(i == 'X'){
result = (prev == 'I') ? result-roman[prev]+9 : result + 10;
} else if(i == 'V'){
result = (prev == 'I') ? result-roman[prev]+4 : result + 5;
} else if(i == 'I'){
result += 1;
}
prev = i;
}
return result;
};