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Roman numerals are represented by seven different symbols:
I
,V
,X
,L
,C
,D
andM
.Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1000
For example, two is written as
II
in 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 not
IIII
. 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:
I
can be placed beforeV
(5) andX
(10) to make 4 and 9.X
can be placed beforeL
(50) andC
(100) to make 40 and 90.C
can 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;
};