OraQA

The following SQL pattern can be used to generate all strings of balanced parentheses.

variable input number

—————————-SQL Solution ————————–

SELECT str
FROM
(SELECT CASE WHEN instr(str,')(') = 0
	     THEN 'F'
             ELSE 'T' END flag, str FROM (SELECT rpad('()', &input * 2,'()') str from dual )
)
MODEL
DIMENSION BY (0 dim)
MEASURES(str, flag)
RULES ITERATE (10000) UNTIL (instr(str[ITERATION_NUMBER+1],')(') = 0 OR flag[0] = 'F')
(
 str[ITERATION_NUMBER+1] =
 CASE WHEN instr(str[cv()-1],')(') >0
      THEN CASE WHEN instr(substr(str[cv()-1],1,instr(str[cv()-1],')(')-1),'()')>0
		THEN rpad('()',least(length(replace(substr(str[cv()-1],1,instr(str[cv()-1],')(')-1),')')),
		                length(replace(substr(str[cv()-1],1,instr(str[cv()-1],')(')-1),'(')))*2,'()')
		    ||CASE WHEN length(replace(substr(str[cv()-1],1,instr(str[cv()-1],')(')-1),')')) =
				least(length(replace(substr(str[cv()-1],1,instr(str[cv()-1],')(')-1),')')),
	                        length(replace(substr(str[cv()-1],1,instr(str[cv()-1],')(')-1),'(')))
                           THEN rpad(')', abs(length(replace(substr(str[cv()-1],1,instr(str[cv()-1],')(')-1),')'))
	                         - length(replace(substr(str[cv()-1],1,instr(str[cv()-1],')(')-1),'(')) ),')')
	                   ELSE rpad('(', abs(length(replace(substr(str[cv()-1],1,instr(str[cv()-1],')(')-1),')'))
	                         - length(replace(substr(str[cv()-1],1,instr(str[cv()-1],')(')-1),'('))),'(')
                       END||'()'||substr(str[cv()-1], instr(str[cv()-1],')(')+2   )
		 ELSE substr(str[cv()-1],1,instr(str[cv()-1],')(')-1)||'()'||
		      substr(str[cv()-1],instr(str[cv()-1],')(')+2)
		END
END
);

Enter value for input: 5
old   5:              ELSE 'T' END flag, str FROM (SELECT rpad('()', &input * 2,'()') str from dual )
new   5:              ELSE 'T' END flag, str FROM (SELECT rpad('()', 5 * 2,'()') str from dual )

STR
----------
()()()()()
(())()()()
()(())()()
(()())()()
((()))()()
()()(())()
(())(())()
()(()())()
(()()())()
((())())()
()((()))()                                                                      

STR
----------
(()(()))()
((()()))()
(((())))()
()()()(())
(())()(())
()(())(())
(()())(())
((()))(())
()()(()())
(())(()())
()(()()())                                                                      

STR
----------
(()()()())
((())()())
()((())())
(()(())())
((()())())
(((()))())
()()((()))
(())((()))
()(()(()))
(()()(()))
((())(()))                                                                      

STR
----------
()((()()))
(()(()()))
((()()()))
(((())()))
()(((())))
(()((())))
((()(())))
(((()())))
((((()))))                                                                      

42 rows selected.

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