Solution 1 - Reverse Build (Group from End)

Remove dashes, uppercase, then build groups of size k from right to left.

TimeComplexity: O(n)

SpaceComplexity: O(n)

""" 0482.1 - License Key Formatting - Solution 1 - Reverse Build """

class Solution:
    def licenseKeyFormatting(self, s: str, k: int) -> str:
        cleaned = s.replace("-", "").upper()
        out = []
        cnt = 0

        for ch in reversed(cleaned):
            if cnt == k:
                out.append("-")
                cnt = 0
            out.append(ch)
            cnt += 1

        return "".join(reversed(out))

if __name__ == "__main__":
    print(Solution().licenseKeyFormatting("5F3Z-2e-9-w", 4))  # 5F3Z-2E9W

function licenseKeyFormatting(s,k){
 const cleaned=s.replace(/-/g,'').toUpperCase();
 let out=[], cnt=0;
 for(let i=cleaned.length-1;i>=0;i--){
  if(cnt===k){ out.push('-'); cnt=0; }
  out.push(cleaned[i]); cnt++;
 }
 return out.reverse().join('');
}

function licenseKeyFormatting(s:string,k:number):string{
 const cleaned=s.replace(/-/g,'').toUpperCase();
 const out:string[]=[];
 let cnt=0;
 for(let i=cleaned.length-1;i>=0;i--){
  if(cnt===k){ out.push('-'); cnt=0; }
  out.push(cleaned[i]); cnt++;
 }
 return out.reverse().join('');
}

package main

import "strings"

func licenseKeyFormatting(s string, k int) string {
	cleaned := strings.ToUpper(strings.ReplaceAll(s, "-", ""))
	out := make([]byte, 0, len(cleaned)+len(cleaned)/k)

	cnt := 0
	for i := len(cleaned) - 1; i >= 0; i-- {
		if cnt == k {
			out = append(out, '-')
			cnt = 0
		}
		out = append(out, cleaned[i])
		cnt++
	}

	for i, j := 0, len(out)-1; i < j; i, j = i+1, j-1 {
		out[i], out[j] = out[j], out[i]
	}
	return string(out)
}

func main() {}

fn license_key_formatting(s: &str, k: usize) -> String {
	let cleaned: Vec<char> = s.chars().filter(|&c| c != '-').map(|c| c.to_ascii_uppercase()).collect();
	let mut out: Vec<char> = vec![];
	let mut cnt = 0usize;

	for &ch in cleaned.iter().rev() {
		if cnt == k {
			out.push('-');
			cnt = 0;
		}
		out.push(ch);
		cnt += 1;
	}
	out.iter().rev().collect()
}
fn main() {}

0482 - License Key Formatting

Solution 1 - Reverse Build (Group from End)