If there is no vowel in the subsequence yet , add vowel at current index if it is ' a ' , else move on to the next character in the string
else if ( subList . size ( ) == 0 ) { if ( str [ index ] != ' a ' ) return longestSubsequence ( str , " " , index + 1 ) ; else return longestSubsequence ( str , subList + str [ index ] , index + 1 ) ; }