class Solution {
public int romanToInt(String s) {
int ans = 0;
for(int i = 0;i < s.length();i++){
if(i == s.length()-1 || getVal(s.charAt(i)) >= getVal(s.charAt(i+1))){
ans += getVal(s.charAt(i));
}else{
ans += getVal(s.charAt(i+1))-getVal(s.charAt(i));
i++;
}
}
return ans;
}
public int getVal(char c){
switch(c){
case 'I': return 1;
case 'V': return 5;
case 'X': return 10;
case 'L': return 50;
case 'C': return 100;
case 'D': return 500;
case 'M': return 1000;
default : return 0;
}
}
}
Q.E.D.