Fix is valid pinyin method

build.gradle.kts

@@ -5,7 +5,7 @@ plugins {
 }
 
 group = "com.marvinelsen"
-version = "1.0-SNAPSHOT"
+version = "1.1-SNAPSHOT"
 
 repositories {
     mavenCentral()

src/main/kotlin/com/marvinelsen/chinese/transliteration/Syllable.kt

@@ -15,7 +15,9 @@ data class Syllable(
         private val zhuyinToneMarkRegex = """[ˊˇˋ˙]""".toRegex()
 
         fun isValidPinyinWithToneNumberSyllable(pinyinSyllable: String) =
-            pinyinSyllable.last().isDigit() && pinyinSyllable.last().digitToInt() in 1..5 && pinyinSyllable.lowercase() in pinyinToZhuyin
+            pinyinSyllable.last().isDigit() && pinyinSyllable.last().digitToInt() in 1..5 && pinyinSyllable
+                .substring(0, pinyinSyllable.lastIndex)
+                .lowercase() in pinyinToZhuyin
 
         fun fromPinyinWithToneNumber(pinyinWithToneNumber: String): Syllable {
             val pinyinWithoutNumber = pinyinWithToneNumber.substring(0, pinyinWithToneNumber.lastIndex)
@@ -45,7 +47,7 @@ data class Syllable(
             return Syllable(
                 zhuyinToPinyin[zhuyinWithoutToneMark]!!,
                 Tone.fromZhuyinToneMarkOrNull(zhuyin.last()) ?: Tone.fromZhuyinToneMarkOrNull(zhuyin.first())
-                    ?: Tone.FIRST
+                ?: Tone.FIRST
             )
         }