Roman to Integer
Given a roman numeral, convert it to an integer.
Input is guaranteed to be within the range from 1 to 3999.
1 public class Solution { 2 public int romanToInt(String s) { 3 if (s == null || s.length()==0) { 4 return 0; 5 } 6 Map<Character, Integer> m = new HashMap<Character, Integer>(); 7 m.put('I', 1); 8 m.put('V', 5); 9 m.put('X', 10); 10 m.put('L', 50); 11 m.put('C', 100); 12 m.put('D', 500); 13 m.put('M', 1000); 14 15 int length = s.length(); 16 int result = m.get(s.charAt(length - 1)); 17 for (int i = length - 2; i >= 0; i--) { 18 if (m.get(s.charAt(i + 1)) <= m.get(s.charAt(i))) { 19 result += m.get(s.charAt(i)); 20 } else { 21 result -= m.get(s.charAt(i)); 22 } 23 } 24 return result; 25 } 26 } 27 28 // 方法二 29 public class Solution { 30 /** 31 * @param s Roman representation 32 * @return an integer 33 */ 34 public int romanToInt(String s) { 35 // Write your code here 36 int ans; 37 char[] sc = s.toCharArray(); 38 ans = toInt(sc[0]); //0 special 39 for (int i = 1; i < s.length(); i++) { 40 ans += toInt(sc[i]); 41 if (toInt(sc[i - 1]) < toInt(sc[i])) { 42 ans -= toInt(sc[i - 1]) * 2; 43 } 44 } 45 return ans; 46 } 47 48 int toInt(char s) { 49 switch(s) { 50 case 'I':return 1; 51 case 'V':return 5; 52 case 'X':return 10; 53 case 'L':return 50; 54 case 'C':return 100; 55 case 'D':return 500; 56 case 'M':return 1000; 57 } 58 return 0; 59 } 60 }