add new solutions

solutions/3/q394/solution.go

@@ -0,0 +1,41 @@
+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