leetcode-go/leetcode/easy/13.go

package main

var mRoman = map[rune]int{
	'I': 1,
	'V': 5,
	'X': 10,
	'L': 50,
	'C': 100,
	'D': 500,
	'M': 1000,
}

func romanToInt(s string) int {
	res := 0
	last := 1000
	for _, v := range s {
		// IV --> V - I
		if last < mRoman[v] {
			res -= 2 * last
		}
		res += mRoman[v]
		last = mRoman[v]
	}
	return res
}