Roman to Integer

Roman to Integer.go

func romanToInt(s string) int {
    numbers := map[string]int{"M":1000, "D":500, "C":100, "L":50, "X":10, "V":5, "I":1}
    last  := -1
    sum := 0
    
    bytes  := []byte(s)
    
    for i := range bytes{
        if last > 0  &&  numbers[string(bytes[i])] > last {
            sum -= 2 * last
        }
        sum += numbers[string(bytes[i])]
        last = numbers[string(bytes[i])]
    }
    
    return sum
 
}