https://leetcode.com/problems/roman-to-integer/
https://leetcode.com/problems/roman-to-integer/discuss/6509/7ms-solution-in-Java.-easy-to-understand
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.https://leetcode.com/problems/roman-to-integer/discuss/6520/JAVA-Easy-Version-To-Understand!!!!
public static int romanToInt(String s) {
if (s == null || s.length() == 0)
return -1;
HashMap<Character, Integer> map = new HashMap<Character, Integer>();
map.put('I', 1);
map.put('V', 5);
map.put('X', 10);
map.put('L', 50);
map.put('C', 100);
map.put('D', 500);
map.put('M', 1000);
int len = s.length(), result = map.get(s.charAt(len - 1));
for (int i = len - 2; i >= 0; i--) {
if (map.get(s.charAt(i)) >= map.get(s.charAt(i + 1)))
result += map.get(s.charAt(i));
else
result -= map.get(s.charAt(i));
}
return result;
}
https://leetcode.com/problems/roman-to-integer/discuss/6509/7ms-solution-in-Java.-easy-to-understand
public int romanToInt(String s) {
int nums[]=new int[s.length()];
for(int i=0;i<s.length();i++){
switch (s.charAt(i)){
case 'M':
nums[i]=1000;
break;
case 'D':
nums[i]=500;
break;
case 'C':
nums[i]=100;
break;
case 'L':
nums[i]=50;
break;
case 'X' :
nums[i]=10;
break;
case 'V':
nums[i]=5;
break;
case 'I':
nums[i]=1;
break;
}
}
int sum=0;
for(int i=0;i<nums.length-1;i++){
if(nums[i]<nums[i+1])
sum-=nums[i];
else
sum+=nums[i];
}
return sum+nums[nums.length-1];
}
http://bangbingsyb.blogspot.com/2014/11/leetcode-roman-to-integer.html