How to Reverse a String in Go: Simple Guide with Example

To reverse a string in Go, convert the string to a slice of runes to handle Unicode characters properly, then swap elements from start to end. Use a loop to reverse the rune slice and convert it back to a string with string().

Syntax

To reverse a string in Go, follow these steps:

• Convert the string to a []rune to support Unicode characters.
• Use a loop to swap runes from the start and end moving towards the center.
• Convert the reversed rune slice back to a string using string().

go

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

Example

This example shows how to reverse a string containing both ASCII and Unicode characters correctly.

go

package main

import (
    "fmt"
)

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

func main() {
    original := "Hello, 世界"
    reversed := reverseString(original)
    fmt.Println("Original:", original)
    fmt.Println("Reversed:", reversed)
}

Output

Original: Hello, 世界
Reversed: 界世 ,olleH

Common Pitfalls

Many beginners try to reverse a string by converting it to a []byte slice, which breaks Unicode characters and causes incorrect output for non-ASCII text.

Always use []rune to handle multi-byte characters properly.

go

package main

import (
    "fmt"
)

// Wrong way: reverses bytes, breaks Unicode
func reverseBytes(s string) string {
    bytes := []byte(s)
    for i, j := 0, len(bytes)-1; i < j; i, j = i+1, j-1 {
        bytes[i], bytes[j] = bytes[j], bytes[i]
    }
    return string(bytes)
}

// Correct way: reverses runes
func reverseRunes(s string) string {
    runes := []rune(s)
    for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 {
        runes[i], runes[j] = runes[j], runes[i]
    }
    return string(runes)
}

func main() {
    s := "Hello, 世界"
    fmt.Println("Wrong reversal:", reverseBytes(s))
    fmt.Println("Correct reversal:", reverseRunes(s))
}

Output

Wrong reversal: 界�,olleH
Correct reversal: 界世 ,olleH

Quick Reference

• Use []rune to handle Unicode characters.
• Swap runes from start to end using a loop.
• Convert runes back to string with string().
• Avoid reversing bytes directly to prevent broken characters.

Key Takeaways

Always convert strings to []rune before reversing to handle Unicode correctly.

Use a loop to swap runes from the start and end moving inward.

Avoid reversing []byte slices directly as it breaks multi-byte characters.

Convert the reversed rune slice back to string using string() function.

Test with Unicode strings to ensure your reversal works correctly.