Roman numerals are represented by seven different symbols: I
, V
, X
, L
, C
, D
and M
.
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 simply X
+ II
. The number twenty seven is written as XXVII
, which is XX
+ 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 as IV
. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as IX
. 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.
Example 1:
Input: "III"
Output: 3
Example 2:
Input: "IV"
Output: 4
Example 3:
Input: "IX"
Output: 9
Example 4:
Input: "LVIII"
Output: 58
Explanation: L = 50, V= 5, III = 3.
Example 5:
Input: "MCMXCIV"
Output: 1994
Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
class Solution {
public:
int romanToInt(string s) {
int ans = ;
int top = ;
int len = s.length();
while(top<len){
if(s[top]=='M'){
ans += ;
top++;
}
else if(s[top]=='D'){
ans += ;
top++;
}
else if(s[top]=='C'){
if(s[top+]=='D'){
ans += ;
top+=;
}
else if(s[top+]=='M'){
ans +=;
top+=;
}
else {
ans += ;
top++;
}
}
else if(s[top]=='L'){
ans+=;
top++;
}
else if(s[top]=='X'){
if(s[top+]=='C'){
ans += ;
top+=;
}
else if(s[top+]=='L'){
ans += ;
top+=;
}
else {
ans += ;
top++;
}
}
else if(s[top]=='V'){
ans+=;
top++;
}
else if(s[top]=='I'){
if(s[top+]=='X'){
ans += ;
top+=;
}
else if(s[top+]=='V'){
ans += ;
top+=;
}
else {
ans += ;
top++;
}
}
}
return ans;
}
};