package main
import (
"fmt"
"unicode"
)
/**
* Reverses only the alphabetic characters in a rune slice in-place,
* leaving special characters, digits, and spaces in their original positions.
*
* @param chars A mutable slice of runes (characters) to modify.
*/
func reverseOnlyLetters(chars []rune) {
if len(chars) == 0 {
return // Guard against empty slices
}
left := 0
right := len(chars) - 1
// Use a two-pointer approach moving inward from both ends
for left < right {
// Advance left pointer until it points to an alphabetic character
for left < right && !unicode.IsLetter(chars[left]) {
left++
}
// Move right pointer backward until it points to an alphabetic character
for left < right && !unicode.IsLetter(chars[right]) {
right--
}
// Swap the valid letters found at both pointers using Go's multi-assignment
if left < right {
chars[left], chars[right] = chars[right], chars[left]
left++
right--
}
}
}
func main() {
// Input string specified
input := "a#b$%c&*(def!"
// Convert string to a slice of runes ([]rune) to support safe Unicode character handling
chars := []rune(input)
fmt.Printf("Original: %s\n", string(chars))
// Apply the reversal function in-place
reverseOnlyLetters(chars)
// Convert the modified rune slice back to a string for display
fmt.Printf("Reversed: %s\n", string(chars))
}
/*
run:
Original: a#b$%c&*(def!
Reversed: f#e$%d&*(cba!
*/
