codewars/go/kyu6/help_the_bookseller/k.go

package kata

import (
	"fmt"
	"strings"
)

func initCounts(listCat []string) map[string]int {
	cats := map[string]int{}
	for _, s := range listCat {
		cats[s[:1]] = 0
	}
	return cats
}

func StockList(listArt []string, listCat []string) string {
	if len(listArt) == 0 || len(listCat) == 0 {
		return ""
	}
	cats := initCounts(listCat)

	var art string
	var count int

	for _, invent := range listArt {
		fmt.Sscanf(invent, "%s %d", &art, &count)
		_, ok := cats[art[:1]]
		if !ok {
			continue
		}
		cats[art[:1]] += count
	}

	slCounts := make([]string, len(cats))
	for i, cat := range listCat {
		slCounts[i] = fmt.Sprintf("(%s : %d)", cat, cats[cat])
		i++
	}

	counts := strings.Join(slCounts, " - ")
	return counts
}