RLE Golang implementation

main.go

package main

import (
	"fmt"
	"strconv"
	"strings"
)

func main() {
	str := "aaaaaabbbbacccccaaabbbbbc"
	encoded := Encode(str)
	fmt.Println(encoded)
	decoded := Decode(encoded)
	fmt.Println(decoded)
	fmt.Println(str)
}

func Encode(raw string) string {
	var prev int32
	var res string
	var count int
	_ = prev
	for idx, chr := range raw {
		if idx == 0 {
			prev = chr
			res += fmt.Sprintf("%s", string(chr))
		}
		if prev != chr {
			res += fmt.Sprintf("%d%s", count, string(chr))
			count = 1
			prev = chr
		} else {
			count++
		}
		if idx == len(raw)-1 {
			res += fmt.Sprintf("%d", count)
		}
	}

	return res
}

var numeric = map[string]struct{}{
	"0": {},
	"1": {},
	"2": {},
	"3": {},
	"4": {},
	"5": {},
	"6": {},
	"7": {},
	"8": {},
	"9": {},
}

func Decode(encoded string) string {
	var count string
	var res string
	var prev string
	for _, chr := range encoded {
		char := string(chr)
		if _, isNumeric := numeric[char]; isNumeric {
			count += char
		} else {
			n, _ := strconv.Atoi(count)
			res += strings.Repeat(prev, n)
			count = ""
			prev = char
		}
	}
	n, _ := strconv.Atoi(count)
	res += strings.Repeat(prev, n)

	return res
}