public static boolean isBalanced ( StringBuilder sb ) {
  Stack < Character > stk = new Stack < > ( ) ;
  stk . add ( sb . charAt ( 0 ) ) ;
  for ( int i = 1 ;
  i < sb . length ( ) ;
  i ++ ) {
    char c = sb . charAt ( i ) ;
    if ( c == ')' ) {
      if ( ! stk . empty ( ) && stk . lastElement ( ) == '(' ) {
        stk . pop ( ) ;
        continue ;
      }
    }
    stk . add ( c ) ;
  }
  return stk . empty ( ) ;
}

public static boolean isBalanced ( StringBuilder sb ) { Stack < Character > stk = new Stack < > ( ) ; stk . add ( sb . charAt ( 0 ) ) ; for ( int i = 1 ; i < sb . length ( ) ; i ++ ) { char c = sb . charAt ( i ) ; if ( c == ' ) ' ) { if ( ! stk . empty ( ) && stk . lastElement ( ) == ' ( ' ) { stk . pop ( ) ; continue ; } } stk . add ( c ) ; } return stk . empty ( ) ; }
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