13. Roman to Integer

Runtime    2 ms
Beats      100%


Memory     43.6 MB
Beats      64.95%


class Solution {
    public int romanToInt(String s) {
        int res=0;
        char st[]=s.toCharArray();
        int n=st.length;

        for(int i=0;i<n;i++){
            if(st[i] == 'I'){
                res+=1;
                if(i+1 < n){
                    if(st[i+1] == 'V'){
                    res+=3;
                    i++;
                }
                    
                else if(st[i+1] == 'X'){
                    res+=8;
                    i++;
                }
                }
            }
            else if(st[i] == 'V')
                res+=5;
            else if(st[i] == 'X'){
                res+=10;
                if(i+1<n){
                    if(st[i+1] == 'L'){
                    res+=30;
                    i++;
                }
                    
                else if(st[i+1] == 'C'){
                    res+=80;
                    i++;
                }
                }
            }
                
            else if(st[i] == 'L')
                res+=50;
            else if(st[i] == 'C'){
                res+=100;
                if(i+1 < n){
                    if(st[i+1] == 'D'){
                    res+=300;
                    i++;
                }
                    
                else if(st[i+1] == 'M'){
                    res+=800;
                    i++;
                }
                }
            }
                
            else if(st[i] == 'D')
                res+=500;
            else if(st[i] == 'M')
                res+=1000;
        }
        return res;
    }
}