33 lines
769 B
Go
33 lines
769 B
Go
//go:build !solution
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package reverse
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import (
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"strings"
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"unicode/utf8"
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)
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// inplace []rune reverse with 2 allocations
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// first for runes slice and second for output
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// func Reverse(input string) string {
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// runes := []rune(input)
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// for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 {
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// runes[i], runes[j] = runes[j], runes[i]
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// }
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// return string(runes)
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// }
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// string.Builder and utf8 decoding magic = 1 allocation
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// overall more iterations but each one is faster,
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// so its as fast as the inplace []rune reverse
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func Reverse(input string) string {
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output := strings.Builder{}
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output.Grow(len(input))
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end := len(input)
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for end > 0 {
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r, n := utf8.DecodeLastRuneInString(input[:end])
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end -= n
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output.WriteRune(r)
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}
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return output.String()
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}
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