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61 lines
1.1 KiB
Go
61 lines
1.1 KiB
Go
// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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// See page 86.
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// Rev reverses a slice.
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package main
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import (
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"bufio"
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"fmt"
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"os"
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"strconv"
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"strings"
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)
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func main() {
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//!+array
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a := [...]int{0, 1, 2, 3, 4, 5}
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reverse(a[:])
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fmt.Println(a) // "[5 4 3 2 1 0]"
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//!-array
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//!+slice
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s := []int{0, 1, 2, 3, 4, 5}
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// Rotate s left by two positions.
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reverse(s[:2])
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reverse(s[2:])
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reverse(s)
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fmt.Println(s) // "[2 3 4 5 0 1]"
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//!-slice
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// Interactive test of reverse.
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input := bufio.NewScanner(os.Stdin)
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outer:
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for input.Scan() {
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var ints []int
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for _, s := range strings.Fields(input.Text()) {
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x, err := strconv.ParseInt(s, 10, 64)
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if err != nil {
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fmt.Fprintln(os.Stderr, err)
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continue outer
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}
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ints = append(ints, int(x))
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}
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reverse(ints)
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fmt.Printf("%v\n", ints)
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}
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// NOTE: ignoring potential errors from input.Err()
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}
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//!+rev
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// reverse reverses a slice of ints in place.
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func reverse(s []int) {
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for i, j := 0, len(s)-1; i < j; i, j = i+1, j-1 {
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s[i], s[j] = s[j], s[i]
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}
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}
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//!-rev
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