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cleaned up code

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This commit is contained in:
Branden Colen
2021-04-05 21:48:17 -05:00
parent 73a2c14edb
commit 1823dc2593
1 changed files with 36 additions and 41 deletions
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romannumeral.go
+36 -41
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@@ -10,46 +10,41 @@ import (
"errors"
)
const (
_maxRoman = 3999
_minRoman = 1
)
var (
InvalidRomanNumeral = errors.New("invalid roman numeral")
IntegerOutOfBounds = errors.New("integer must be between 1 and 3999")
)
// numeral describes the value and symbol of a single roman numeral
type numeral struct {
val int
sym []byte
}
// _numerals are all unique numerals ordered from largest to smallest
var _numerals = []numeral{
{1000, []byte("M")},
{900, []byte("CM")},
{500, []byte("D")},
{400, []byte("CD")},
{100, []byte("C")},
{90, []byte("XC")},
{50, []byte("L")},
{40, []byte("XL")},
{10, []byte("X")},
{9, []byte("IX")},
{5, []byte("V")},
{4, []byte("IV")},
{1, []byte("I")},
}
// lookup arrays used for converting from an int to a roman numeral extremely quickly.
// method from here: https://rosettacode.org/wiki/Roman_numerals/Encode#Go
var (
m0 = []string{"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"}
m1 = []string{"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"}
m2 = []string{"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"}
m3 = []string{"", "M", "MM", "MMM"}
// InvalidRomanNumeral - error for when a roman numeral string provided is not a valid roman numeral
InvalidRomanNumeral = errors.New("invalid roman numeral")
// IntegerOutOfBounds - error for when the integer provided is invalid and unable to be converted to a roman numeral
IntegerOutOfBounds = errors.New("integer must be between 1 and 3999")
// all unique numerals ordered from largest to smallest
nums = []numeral{
{1000, []byte("M")},
{900, []byte("CM")},
{500, []byte("D")},
{400, []byte("CD")},
{100, []byte("C")},
{90, []byte("XC")},
{50, []byte("L")},
{40, []byte("XL")},
{10, []byte("X")},
{9, []byte("IX")},
{5, []byte("V")},
{4, []byte("IV")},
{1, []byte("I")},
}
// lookup arrays used for converting from an int to a roman numeral extremely quickly.
// method from here: https://rosettacode.org/wiki/Roman_numerals/Encode#Go
r0 = []string{"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"}
r1 = []string{"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"}
r2 = []string{"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"}
r3 = []string{"", "M", "MM", "MMM"}
)
// IntToString converts an integer value to a roman numeral string. An error is
@@ -71,13 +66,13 @@ func IntToBytes(input int) ([]byte, error) {
// outOfBounds checks to ensure an input value is valid for roman numerals without the need of
// vinculum (used for values of 4,000 and greater)
func outOfBounds(input int) bool {
return input < _minRoman || input > _maxRoman
return input < 1 || input > 3999
}
func intToRoman(n int) string {
// This is efficient in Go. The 4 operands are evaluated,
// then a single allocation is made of the exact size needed for the result.
return m3[n%1e4/1e3] + m2[n%1e3/1e2] + m1[n%100/10] + m0[n%10]
return r3[n%1e4/1e3] + r2[n%1e3/1e2] + r1[n%100/10] + r0[n%10]
}
// StringToInt converts a roman numeral string to an integer. Roman numerals for numbers
@@ -102,13 +97,13 @@ func BytesToInt(input []byte) (int, error) {
func romanToInt(input []byte) (int, bool) {
var output int
for _, rom := range _numerals {
for bytes.HasPrefix(input, rom.sym) {
output += rom.val
input = input[len(rom.sym):]
for _, n := range nums {
for bytes.HasPrefix(input, n.sym) {
output += n.val
input = input[len(n.sym):]
}
}
// If we are still left with input string values then the
// input was invalid and the bool is returned as False
// if we are still left with input string values then the
// input was invalid and the bool is returned as false
return output, len(input) == 0
}