40 lines
1.3 KiB
Go
40 lines
1.3 KiB
Go
package main
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import "fmt"
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var (
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m0 = []string{"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"}
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m1 = []string{"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"}
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m2 = []string{"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"}
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m3 = []string{"", "M", "MM", "MMM", "I̅V̅",
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"V̅", "V̅I̅", "V̅I̅I̅", "V̅I̅I̅I̅", "I̅X̅"}
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m4 = []string{"", "X̅", "X̅X̅", "X̅X̅X̅", "X̅L̅",
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"L̅", "L̅X̅", "L̅X̅X̅", "L̅X̅X̅X̅", "X̅C̅"}
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m5 = []string{"", "C̅", "C̅C̅", "C̅C̅C̅", "C̅D̅",
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"D̅", "D̅C̅", "D̅C̅C̅", "D̅C̅C̅C̅", "C̅M̅"}
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m6 = []string{"", "M̅", "M̅M̅", "M̅M̅M̅"}
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)
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func formatRoman(n int) (string, bool) {
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if n < 1 || n >= 4e6 {
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return "", false
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}
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// this is efficient in Go. the seven operands are evaluated,
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// then a single allocation is made of the exact size needed for the result.
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return m6[n/1e6] + m5[n%1e6/1e5] + m4[n%1e5/1e4] + m3[n%1e4/1e3] +
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m2[n%1e3/1e2] + m1[n%100/10] + m0[n%10],
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true
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}
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func main() {
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// show three numbers mentioned in task descriptions
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for _, n := range []int{1990, 2008, 1666} {
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r, ok := formatRoman(n)
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if ok {
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fmt.Println(n, "==", r)
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} else {
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fmt.Println(n, "not representable")
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}
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}
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}
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