package q394

import "strings"

func decode(s string) (int, string) {
	advanced := 0
	number := 0
	buf := strings.Builder{}

Loop:
	for advanced < len(s) {
		advanced++
		cur := s[advanced-1]
		switch {
		case cur >= '0' && cur <= '9':
			number = 10*number + int(cur-'0')

		case cur == '[':
			adv, child := decode(s[advanced:])
			advanced += adv
			for range number {
				buf.WriteString(child)
			}
			number = 0

		case cur == ']':
			break Loop

		default:
			buf.WriteByte(cur)
		}
	}
	return advanced, buf.String()
}

func decodeString(s string) string {
	_, ret := decode(s)
	return ret
}

var _ = decodeString