[LeetCode]13、Roman to Integer

题目描述：

Given a roman numeral, convert it to an integer.

Input is guaranteed to be within the range from 1 to 3999.

思路：

罗马数字转int 遍历string，如果左边大于右边，则加上右边，如果小于，则减去用sum记录结果

 1 public class Solution13{
 2     public int romanToInt(String s){
 3         HashMap<Character, Integer> map = new HashMap<>();
 4         map.put('I', 1);
 5         map.put('V', 5);
 6         map.put('X', 10);
 7         map.put('L', 50);
 8         map.put('C', 100);
 9         map.put('D', 500);
10         map.put('M', 1000);
11         int sum = 0;
12         
13         for(int i = 0;i < s.length();i++){
14             //int value = map.get(s.charAt(i));
15             if(i == s.length()-1 || map.get(s.charAt(i+1))<=map.get(s.charAt(i))){
16                 sum += map.get(s.charAt(i));
17             }
18             else {
19                 sum -= map.get(s.charAt(i));    
20             }
21         }
22         return sum;
23     }
24     public static void main(String[] args) {
25         // TODO Auto-generated method stub
26         Solution13 solution13 = new Solution13();
27         System.out.println(solution13.romanToInt("XLVI"));
28     }
29 }