static int productAtKthLevel ( String tree , int k ) {
  int level = - 1 ;
  int product = 1 ;
  int n = tree . length ( ) ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    if ( tree . charAt ( i ) == '(' ) level ++ ;
    else if ( tree . charAt ( i ) == ')' ) level -- ;
    else {
      if ( level == k ) product *= ( tree . charAt ( i ) - '0' ) ;
    }
  }
  return product ;
}

static int productAtKthLevel ( String tree , int k ) { int level = - 1 ; int product = 1 ; int n = tree . length ( ) ; for ( int i = 0 ; i < n ; i ++ ) { if ( tree . charAt ( i ) == ' ( ' ) level ++ ; else if ( tree . charAt ( i ) == ' ) ' ) level -- ; else { if ( level == k ) product *= ( tree . charAt ( i ) - '0' ) ; } } return product ; }
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