将字符串转换为字母数字[关闭]

Question

I want to find if there is a better way to convert a given string to alpha numeric than to go by ascii value range as I am doing in the following code. It works as expected but wondering if there is a cleaner way to do this.

Also my function buildAlphaN() converts string to lowercase to do the checks that follow.

if input: "A man, a plan, a canal: Panama" then output from buildAlphaN(): amanaplanacanalpanama

I have the whole solution for the problem for context, but my question is purely for the buildAlphaN() function.

// spaces part of palindrome? - ignored. 
import "strings"

//builds alphan and returns lower case
func buildAlphaN(s string) string {
    res := ""
    for _, v := range s {
         //0-9, A-Z, a-z
        if (v >= 48 && v <=57) || (v >= 65 && v <= 90) || (v >= 97 && v <= 122) {
            res += string(v)
        } 
    } 

    return strings.ToLower(res) 
}

func isPalindrome(s string) bool {
    if len(s) == 0 {
        //empty string
        return true
    } 

    s2 := buildAlphaN(s)
    fmt.Printf("s:%v s2:%v
", s, s2)

    if palindromeCheck(s2) == true {
        return true
    }
    return false 
}

func  palindromeCheck(s string) bool {
    if len(s) == 1 {
        return true
    }

    for i, j := 0, len(s) - 1; i < j; i,j = i+1, j-1 {
        if s[i] == s[j] {
            continue
        } else {
            return false 
        } 
    }  
    return true
}

Answer 1

For example,

package main

import (
    "fmt"
    "unicode"
)

func isPalindrome(s string) bool {
    rs := make([]rune, 0, len(s))
    for _, r := range s {
        if unicode.IsLetter(r) || unicode.IsNumber(r) {
            rs = append(rs, unicode.ToLower(r))
        }
    }

    for i, j := 0, len(rs)-1; i < j; i, j = i+1, j-1 {
        if rs[i] != rs[j] {
            return false
        }
    }
    return true
}

func main() {
    s := "A man, a plan, a canal: Panama"
    fmt.Println(isPalindrome(s))
}

Output:

true