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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, 2
is written as II
in Roman numeral, just two one's added together. 12
is written as XII
, which is simply X + II
. The number 27
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 before V
(5) and X
(10) to make 4 and 9. X
can be placed before L
(50) and C
(100) to make 40 and 90. C
can be placed before D
(500) and M
(1000) to make 400 and 900.Given a roman numeral, convert it to an integer.
Example 1:
Input: s = "III" Output: 3
Example 2:
Input: s = "IV" Output: 4
Example 3:
Input: s = "IX" Output: 9
Example 4:
Input: s = "LVIII" Output: 58 Explanation: L = 50, V= 5, III = 3.
Example 5:
Input: s = "MCMXCIV" Output: 1994 Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
Constraints:
1 <= s.length <= 15
s
contains only the characters ('I', 'V', 'X', 'L', 'C', 'D', 'M')
.s
is a valid roman numeral in the range [1, 3999]
.class Solution:
def romanToInt(self, s: str) -> int:
nums = {
'M': 1000,
'CM': 900,
'D': 500,
'CD': 400,
'C': 100,
'XC': 90,
'L': 50,
'XL': 40,
'X': 10,
'IX': 9,
'V': 5,
'IV': 4,
'I': 1
}
i = res = 0
while i < len(s):
if i + 1 < len(s) and s[i:i + 2] in nums:
res += nums[s[i: i + 2]]
i += 2
else:
res += nums[s[i: i + 1]]
i += 1
return res
class Solution {
public int romanToInt(String s) {
Map<String, Integer> nums = new HashMap<>();
nums.put("M", 1000);
nums.put("CM", 900);
nums.put("D", 500);
nums.put("CD", 400);
nums.put("C", 100);
nums.put("XC", 90);
nums.put("L", 50);
nums.put("XL", 40);
nums.put("X", 10);
nums.put("IX", 9);
nums.put("V", 5);
nums.put("IV", 4);
nums.put("I", 1);
int res = 0;
for (int i = 0; i < s.length();) {
if (i + 1 < s.length() && nums.get(s.substring(i, i + 2)) != null) {
res += nums.get(s.substring(i, i + 2));
i += 2;
} else {
res += nums.get(s.substring(i, i + 1));
i += 1;
}
}
return res;
}
}
class Solution {
public:
int romanToInt(string s) {
unordered_map<char, int> nums{
{'I', 1},
{'V', 5},
{'X', 10},
{'L', 50},
{'C', 100},
{'D', 500},
{'M', 1000},
};
int ans = 0;
for (int i = 0; i < s.size() - 1; ++i) {
if (nums[s[i]] < nums[s[i + 1]])
ans -= nums[s[i]];
else
ans += nums[s[i]];
}
return ans + nums[s.back()];
}
};
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