42 lines
975 B
Go
42 lines
975 B
Go
package main
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import (
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"math"
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"strings"
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)
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const (
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// characters used for short-urls
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SYMBOLS = "0123456789abcdefghijklmnopqrsuvwxyzABCDEFGHIJKLMNOPQRSTUVXYZ"
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// someone set us up the bomb !!
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BASE = int64(len(SYMBOLS))
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)
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// encodes a number into our *base* representation
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// TODO can this be made better with some bitshifting?
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func Encode(number int64) string {
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rest := number % BASE
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// strings are a bit weird in go...
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result := string(SYMBOLS[rest])
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if number-rest != 0 {
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newnumber := (number - rest) / BASE
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result = Encode(newnumber) + result
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}
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return result
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}
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// Decodes a string given in our encoding and returns the decimal
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// integer.
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func Decode(input string) int64 {
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const floatbase = float64(BASE)
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l := len(input)
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var sum int = 0
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for index := l - 1; index > -1; index -= 1 {
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current := string(input[index])
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pos := strings.Index(SYMBOLS, current)
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sum = sum + (pos * int(math.Pow(floatbase, float64((l-index-1)))))
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}
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return int64(sum)
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}
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