Leetcode004 -- Roman numeral to integer

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class test04 {

    /**
     * 13.  Roman numeral to integer 
     *  Roman numerals contain the following seven characters : I, V, X, L,C,D  and  M.
     *
     *  character            The number 
     * I             1
     * V             5
     * X             10
     * L             50
     * C             100
     * D             500
     * M             1000
     *  for example ,  Rome digital  2  Write to do  II , Two parallel  1 .12  Write to do  XII , That is to say  X + II . 27  Write to do   XXVII,  That is to say  XX + V + II .
     *  Usually , The small numbers in roman numbers are to the right of the big ones . But there are special cases , for example  4  Do not write  IIII, It is  IV. Numbers  1  In number  5  Left side , The number represented is equal to the large number  5  Decimal reduction  1  Value obtained  4 . similarly , Numbers  9  Expressed as  IX. This special rule only applies to the following six cases ：
     *
     * I  Can be placed in  V (5)  and  X (10)  Left side , To express  4  and  9.
     * X  Can be placed in  L (50)  and  C (100)  Left side , To express  40  and  90.
     * C  Can be placed in  D (500)  and  M (1000)  Left side , To express  400  and  900.
     *  Given a Roman number , 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
     *  explain : L = 50, V= 5, III = 3.
     *
     *  Example  5:
     *  Input : s = "MCMXCIV"
     *  Output : 1994
     *  explain : M = 1000, CM = 900, XC = 90, IV = 4.
     *
     *  Tips ：
     * 1 <= s.length <= 15
     * s  Characters only  ('I', 'V', 'X', 'L', 'C', 'D', 'M')
     *  Topic data assurance  s  It's a valid Roman number , And it means that the integer is in the range  [1, 3999]  Inside 
     *  The test cases given in the title all conform to the Roman numeral writing rules , There will be no straddle, etc .
     * IL  and  IM  Such an example does not meet the requirements of the title ,49  You should write  XLIX,999  You should write  CMXCIX .
     *  Detailed rules for writing Roman numerals , You can refer to   Rome digital  - Mathematics .
      * @param args
     */
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        System.out.println(" Please enter Roman numerals ：");
        String romanStr = sc.nextLine();

        System.out.println(romanToInt(romanStr));

    }

    public static int romanToInt(String roamnStr){
        Map<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 res = 0;
        for(int i=0; i<roamnStr.length(); i++){
            if(map.containsKey(roamnStr.charAt(i)) && i<roamnStr.length()-1 && map.get(roamnStr.charAt(i))<map.get(roamnStr.charAt(i+1))){
                res -= map.get(roamnStr.charAt(i));
            }else{
                res += map.get(roamnStr.charAt(i));
            }
        }
        return res;
    }
}