RomanInteger

//Given a roman numeral, convert it to an integer.
//
//Input is guaranteed to be within the range from 1 to 3999.
//最后一个用来赋初值，前面的如果大于或等于就加上去，小于就减去这个
import java.util.HashMap;
import java.util.Map;


public class RomanInteger {
public int romanToInt(String s) {
 Map map=new HashMap<>();
  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 result=0;
  for (int i = s.length()-1; i>=0; i--) {
if(i == s.length()-1){
result=map.get(s.substring(i, i+1));
continue;
}
if(map.get(s.substring(i, i+1))>=map.get(s.substring(i+1, i+2)))
result+=map.get(s.substring(i, i+1));
else 
result-=map.get(s.substring(i, i+1));

  }
  return result;
}
    
}