13.罗马数字转整数.md

title	categories
罗马数字转整数	leetcode leetcode题解

package main

/*
 * @lc app=leetcode.cn id=13 lang=golang
 *
 * [13] 罗马数字转整数

 2. I X C 也是写成从大到小
 3. 左高位，右低位
 4. 输入: s = "MC MX CI V"
             1100 1010 101 5
	输出: 1994
	解释: M = 1000, CM = 900, XC = 90, IV = 4.

	MMMCCCXXXIII
	1000+1000+1000 -100-100-100-10-10-10+1+1+1
	CXCIX
	100 -10 +100-1+10
*/

// @lc code=start
func romanToInt(s string) int {

	var intSum int
	for i := 0; i < len(s)-1; i++ {
		if char2Int(string(s[i])) > char2Int(string(s[i+1])) {
			intSum = intSum + char2Int(string(s[i]))
		} else if char2Int(string(s[i])) < char2Int(string(s[i+1])) {
			intSum = intSum - char2Int(string(s[i]))
		} else {
			intSum = intSum + char2Int(string(s[i]))
		}
	}
	intSum = intSum + char2Int(string(s[len(s)-1]))

	return intSum

}
func char2Int(c string) int {
	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
	}
	panic("excep I V X L C D M")
}

// @lc code=end