Balanced brackets: Difference between revisions
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$$ MODE DATA |
$$ MODE DATA |
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$$ SET brackets=* |
$$ SET brackets=* |
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[ |
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[ |
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[] |
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[] |
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][ |
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][ |
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[]] |
[]] |
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][][ |
][][ |
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][][] |
][][] |
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[[[]][ |
[[[]][ |
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[]][[[] |
[]][[[] |
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][][][[] |
][][][[] |
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][]][][[] |
][]][][[] |
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[]][[]][[] |
[]][[]][[] |
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][[]]][]]][ |
][[]]][]]][ |
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[[]][[[[]]]] |
[[]][[[[]]]] |
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[[]] |
[[]] |
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[[[[]]]] |
[[[[]]]] |
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[[]][][]]]][[ |
[[]][][]]]][[ |
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_____________ |
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$$ BUILD X_TABLE brackets=* |
$$ BUILD X_TABLE brackets=* |
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[[[[ (4 ]]]] )4 |
[[[[ (4 ]]]] )4 |
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$$ MODE TUSCRIPT |
$$ MODE TUSCRIPT |
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LOOP b=brackets |
LOOP b=brackets |
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status=CHECK_BRACKETS (b,brackets,a1,e1,a2,e2) |
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PRINT |
PRINT b," ",status |
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ENDLOOP |
ENDLOOP |
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</lang> |
</lang> |
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Output: |
Output: |
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<pre style='height:30ex;overflow:scroll'> |
<pre style='height:30ex;overflow:scroll'> |
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[ ERROR |
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ERROR [ |
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[] OK |
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OK [] |
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][ ERROR |
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ERROR ][ |
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[]] ERROR |
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][][ ERROR |
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][][] ERROR |
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[[[]][ ERROR |
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[]][[[] ERROR |
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][][][[] ERROR |
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][]][][[] ERROR |
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[]][[]][[] ERROR |
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][[]]][]]][ ERROR |
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[[]][[[[]]]] OK |
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[[]] OK |
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[[[[]]]] OK |
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[[]][][]]]][[ ERROR |
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_____________ OK |
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OK |
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</pre> |
</pre> |
Revision as of 20:23, 20 February 2011
You are encouraged to solve this task according to the task description, using any language you may know.
Task:
- Generate a string with
$N
opening brackets ("["
) and$N
closing brackets ("]"
), in some arbitrary order. - Determine whether the string is balanced; that is, whether it consists entirely of pairs of opening/closing brackets (in that order), none of which mis-nest.
Examples:
(empty) OK [] OK ][ NOT OK [][] OK ][][ NOT OK [[][]] OK []][[] NOT OK
D
<lang d>import std.stdio, std.algorithm, std.string,
std.range, std.random, std.conv;
auto generate(int n) {
return text(map!((i){ return "[]"[uniform(0,2)]; })(iota(n)));
}
void main() {
foreach (i; 0 .. 14) { auto s = generate(i); writefln("%-15s is%s balanced", '"' ~ s ~ '"', s.balancedParens('[', ']') ? "" : " not"); }
}</lang> Output:
"" is balanced "[" is not balanced "][" is not balanced "[]]" is not balanced "][][" is not balanced "][][]" is not balanced "[[[]][" is not balanced "[]][[[]" is not balanced "][][][[]" is not balanced "][]][][[]" is not balanced "[]][[]][[]" is not balanced "][[]]][]]][" is not balanced "[[]][[[[]]]]" is balanced "[[]][][]]]][[" is not balanced
J
Solution: <lang j>pbal =: _1 *./ . < '[]' -&(+/\)/@:(=/) ]</lang> Examples:<lang j> 'TESTS EXPECTED'=:( a:"_`0:`[} ,&< (<'OK') = ])/ |: cut;._2 noun define (empty) OK [] OK ][ BAD [][] OK ][][ BAD ]][[ BAD [[][]] OK []][[] BAD ]]][[[ BAD [][][[]] OK [[[][[]]]] OK [][][[][]][] OK [[]][]]]][[[][ BAD ][][[][][][[]]][ BAD ][[[][]][]]][][[][ BAD ]][][]][[][[][[]][][ BAD [[[][[][]]][]]][[]]][[ BAD [[]]][]][[[[]]][[][][[]] BAD ][[][][]][[[]][[[[][]]]][] BAD ]][[][[][[[[]][[][]][[]]]]][ BAD )
EXPECTED -: pbal &> TESTS
1</lang> Comments: This task highlights the versatility and usefulness of J's scanning modifiers, / and \.
Perl 6
<lang perl6>sub balanced($s) {
my $l = 0; for $s.comb { when "]" { --$l; return False if $l < 0; } when "[" { ++$l; } } return $l == 0;
}
my $N = get; my $s = (<[ ]> xx $N).pick(*).join; say "$s {balanced($s) ?? "is" !! "is not"} well-balanced"</lang>
PureBasic
<lang PureBasic>Procedure.s Generate(N)
For i=1 To N sample$+"[]" Next For i=Len(sample$)-1 To 2 Step -1 r=Random(i-1)+1 If r<>i a.c=PeekC(@sample$+r*SizeOf(Character)) b.c=PeekC(@sample$+i*SizeOf(Character)) PokeC(@sample$+r*SizeOf(Character), b) PokeC(@sample$+i*SizeOf(Character), a) EndIf Next ProcedureReturn sample$
EndProcedure
Procedure Balanced(String$)
Protected *p.Character, cnt *p=@String$ While *p\c If *p\c='[' cnt+1 ElseIf *p\c=']' cnt-1 If cnt<0: Break: EndIf EndIf *p+SizeOf(Character) Wend If cnt=0 ProcedureReturn #True EndIf
EndProcedure
- - Test code
OpenConsole() For i=1 To 5
TestString$ = Generate(i) Print(TestString$) If Balanced(TestString$) PrintN(" is ballanced.") Else PrintN(" is not ballanced") EndIf
Next</lang> Output sample
[] is ballanced. [[]] is ballanced. [[[]]] is ballanced. [][]]][[ is not ballanced [][][][]][ is not ballanced
Python
<lang python>>>> def gen(N): ... txt = ['['] * N + [']'] * N ... random.shuffle( txt ) ... return .join(txt) ... >>> def balanced(txt): ... braced = 0 ... for ch in txt: ... if ch == '[': braced += 1 ... if ch == ']': ... braced -= 1 ... if braced < 0: return False ... return braced == 0 ... >>> for txt in (gen(N) for N in range(10)): ... print ("%-22r is%s balanced" % (txt, if balanced(txt) else ' not')) ... is balanced '[]' is balanced '[][]' is balanced '][[[]]' is not balanced '[]][[][]' is not balanced '[][[][]]][' is not balanced '][]][][[]][[' is not balanced '[[]]]]][]][[[[' is not balanced '[[[[]][]]][[][]]' is balanced '][[][[]]][]]][[[[]' is not balanced</lang>
Tcl
<lang tcl>proc generate {n} {
if {!$n} return set l [lrepeat $n "\[" "\]"] set len [llength $l] while {$len} {
set tmp [lindex $l [set i [expr {int($len * rand())}]]] lset l $i [lindex $l [incr len -1]] lset l $len $tmp
} return [join $l ""]
}
proc balanced s {
set n 0 foreach c [split $s ""] {
# Everything unmatched is ignored, which is what we want switch -exact -- $c { "\[" {incr n} "\]" {if {[incr n -1] < 0} {return false}} }
} expr {!$n}
}
for {set i 0} {$i < 15} {incr i} {
set s [generate $i] puts "\"$s\"\t-> [expr {[balanced $s] ? {OK} : {NOT OK}}]"
}</lang> Sample output:
"" -> OK "][" -> NOT OK "]][[" -> NOT OK "]]][[[" -> NOT OK "[][][[]]" -> OK "[[[][[]]]]" -> OK "[][][[][]][]" -> OK "[[]][]]]][[[][" -> NOT OK "][][[][][][[]]][" -> NOT OK "][[[][]][]]][][[][" -> NOT OK "]][][]][[][[][[]][][" -> NOT OK "[[[][[][]]][]]][[]]][[" -> NOT OK "[[]]][]][[[[]]][[][][[]]" -> NOT OK "][[][][]][[[]][[[[][]]]][]" -> NOT OK "]][[][[][[[[]][[][]][[]]]]][" -> NOT OK
TUSCRIPT
<lang tuscript> $$ MODE DATA $$ SET brackets=*
[ [] ][ []] ][][ ][][] [[[]][ []][[[] ][][][[] ][]][][[] []][[]][[] ][[]]][]]][ [[]][[[[]]]] [[]] [[[[]]]]
[[]][][]]]][[ _____________ $$ BUILD X_TABLE brackets=*
[[(4 ]] )4 [[[ (3 ]]] )3 (2 )2 [ (1 ] )1
$$ MODE TUSCRIPT LOOP b=brackets status=CHECK_BRACKETS (b,brackets,a1,e1,a2,e2) PRINT b," ",status ENDLOOP </lang> Output:
[ ERROR [] OK ][ ERROR []] ERROR ][][ ERROR ][][] ERROR [[[]][ ERROR []][[[] ERROR ][][][[] ERROR ][]][][[] ERROR []][[]][[] ERROR ][[]]][]]][ ERROR [[]][[[[]]]] OK [[]] OK [[[[]]]] OK [[]][][]]]][[ ERROR _____________ OK