How to reverse a string in Go?

Question

How can we reverse a simple string in Go?

Answer 1

try below code:

package main

import "fmt"

func reverse(s string) string {
    chars := []rune(s)
    for i, j := 0, len(chars)-1; i < j; i, j = i+1, j-1 {
        chars[i], chars[j] = chars[j], chars[i]
    }
    return string(chars)
}

func main() {
    fmt.Printf("%v\n", reverse("abcdefg"))
}

for more info check http://golangcookbook.com/chapters/strings/reverse/
and http://www.dotnetperls.com/reverse-string-go

Answer 2

You could also import an existing implementation:

import "4d63.com/strrev"

Then:

strrev.Reverse("abåd") // returns "dåba"

Or to reverse a string including unicode combining characters:

strrev.ReverseCombining("abc\u0301\u031dd") // returns "d\u0301\u031dcba"

These implementations supports correct ordering of unicode multibyte and combing characters when reversed.

Note: Built-in string reverse functions in many programming languages do not preserve combining, and identifying combining characters requires significantly more execution time.

Answer 3

//Reverse reverses string using strings.Builder. It's about 3 times faster
//than the one with using a string concatenation
func Reverse(in string) string {
    var sb strings.Builder
    runes := []rune(in)
    for i := len(runes) - 1; 0 <= i; i-- {
        sb.WriteRune(runes[i])
    }
    return sb.String()
}


//Reverse reverses string using string
func Reverse(in string) (out string) {
    for _, r := range in {
        out = string(r) + out
    }
    return
}

BenchmarkReverseStringConcatenation-8   1000000 1571 ns/op  176 B/op    29 allocs/op
BenchmarkReverseStringsBuilder-8        3000000 499 ns/op   56 B/op 6 allocs/op

Using strings.Builder is about 3 times faster than using string concatenation

Answer 4

Here is quite different, I would say more functional approach, not listed among other answers:

func reverse(s string) (ret string) {
    for _, v := range s {
        defer func(r rune) { ret += string(r) }(v)
    }
    return
}

Answer 5

func Reverse(s string) string {
    r := []rune(s)
    var output strings.Builder
    for i := len(r) - 1; i >= 0; i-- {
        output.WriteString(string(r[i]))
    }

    return output.String()
}

Answer 6

A version which I think works on unicode. It is built on the utf8.Rune functions:

func Reverse(s string) string {
    b := make([]byte, len(s));
    for i, j := len(s)-1, 0; i >= 0; i-- {
        if utf8.RuneStart(s[i]) {
            rune, size := utf8.DecodeRuneInString(s[i:len(s)]);
            utf8.EncodeRune(rune, b[j:j+size]);
            j += size;
        }
    }
    return string(b);
}