13. Roman to Integer.md

13. Roman to Integer

Thinking:

• Method1:

1. If not exceed the length of string, check if two characters are included in the map, if so, add its represented integer value. Otherwise add the value of one character.

	class Solution {
	    public int romanToInt(String s) {
	        int result = 0;
	        String[] roman = {"M", "CM","D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};
		    int[] n = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
	        Map<String, Integer> m = new HashMap<>();
	        for(int i = 0; i < n.length; i++){
	            m.put(roman[i], n[i]);
	        }
	        int len = s.length();
	        int i = 0;
	        while(i < len){
	            Integer temp = null;
	            if(i+2 <= len){
	                temp = m.get(s.substring(i, i+2));
	                if(null != temp){
	                    result += temp;
	                    i += 2;
	                    continue;
	                }else{
	                    result += m.get(s.substring(i, i+1));
	                    i++;
	                    continue;
	                }
	            }else{
	                result += m.get(s.substring(i, i+1));
	                i ++;
	                continue;
	            }
	        }
	        return result;
	    }
	}