Basic roman<->arabic numerals conversion utils

roman.go

package main

import (
  "sort"
  "strings"
)

var romanIntMap = map[string]int{
  "M": 1000,
  "D": 500,
  "C": 100,
  "L": 50,
  "X": 10,
  "V": 5,
  "I": 1,

  "CM": 900,
  "CD": 400,
  "XC": 90,
  "XL": 40,
  "IX": 9,
  "IV": 4,
}

func RomanToInt(roman string) int {
  n := 0
  var prev = string(roman[0])
  for _, v := range roman {
    s := string(v)
    if prev != s && romanIntMap[prev] < romanIntMap[s] {
      n -= romanIntMap[prev] * 2
    }
    n += romanIntMap[s]
    prev = s
  }
  return n
}

func IntToRoman(n int) string {
  vals := make([]int, len(romanIntMap))
  intRomanMap := make(map[int]string, len(romanIntMap))

  {
    var i uint8 = 0
    for k, v := range romanIntMap {
      intRomanMap[v] = k
      vals[i] = v
      i++
    }
  }
  
  // Sort keys desc
  sort.Slice(vals, func (i, j int) bool { return vals[j] < vals[i] })

  res := ""
  for _, val := range vals {
    sum, i := 0, 0
    
    for n - val >= 0 {
      i++
      n -= val
      sum += val
    }

    if i > 1 {
      res += strings.Repeat(intRomanMap[sum], i)
    } else {
      res += intRomanMap[sum]
    }
  }

  return res
}