[LeetCode]14. Roman to Integer

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 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. 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.
找规律，正常都直接加，只有为4，9这样的情况是减

public int romanToInt(String s) {
        HashMap<Character,Integer> map=new HashMap(){
            {
                put('I',1);
                put('X',10);
                put('C',100);
                put('M',1000);
                put('V',5);
                put('L',50);
                put('D',500);
            }
        };
        int result=0;
        char[] array=s.toCharArray();
        for(int i=0;i<array.length;i++){
            char c=array[i];
            if(i<array.length-1 && map.get(c)<map.get(array[i+1])) result-=map.get(c);
            else result+=map.get(c);
        }
        return result;
}