91 lines
1.7 KiB
Go
91 lines
1.7 KiB
Go
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package main
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import "strings"
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// ConvertToArabic converts a Roman Numeral to an Arabic number.
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func ConvertToArabic(roman string) (total uint16) {
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for _, symbols := range windowedRoman(roman).Symbols() {
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total += allRomanNumerals.ValueOf(symbols...)
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}
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return
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}
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// ConvertToRoman converts an Arabic number to a Roman Numeral.
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func ConvertToRoman(arabic uint16) string {
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var result strings.Builder
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for _, numeral := range allRomanNumerals {
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for arabic >= numeral.Value {
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result.WriteString(numeral.Symbol)
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arabic -= numeral.Value
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}
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}
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return result.String()
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}
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type romanNumeral struct {
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Value uint16
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Symbol string
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}
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type romanNumerals []romanNumeral
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func (r romanNumerals) ValueOf(symbols ...byte) uint16 {
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symbol := string(symbols)
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for _, s := range r {
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if s.Symbol == symbol {
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return s.Value
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}
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}
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return 0
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}
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func (r romanNumerals) Exists(symbols ...byte) bool {
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symbol := string(symbols)
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for _, s := range r {
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if s.Symbol == symbol {
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return true
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}
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}
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return false
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}
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var allRomanNumerals = romanNumerals{
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{1000, "M"},
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{900, "CM"},
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{500, "D"},
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{400, "CD"},
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{100, "C"},
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{90, "XC"},
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{50, "L"},
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{40, "XL"},
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{10, "X"},
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{9, "IX"},
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{5, "V"},
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{4, "IV"},
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{1, "I"},
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}
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type windowedRoman string
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func (w windowedRoman) Symbols() (symbols [][]byte) {
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for i := 0; i < len(w); i++ {
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symbol := w[i]
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notAtEnd := i+1 < len(w)
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if notAtEnd && isSubtractive(symbol) && allRomanNumerals.Exists(symbol, w[i+1]) {
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symbols = append(symbols, []byte{symbol, w[i+1]})
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i++
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} else {
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symbols = append(symbols, []byte{symbol})
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}
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}
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return
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}
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func isSubtractive(symbol uint8) bool {
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return symbol == 'I' || symbol == 'X' || symbol == 'C'
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}
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