Balanced brackets: Difference between revisions
→{{header|Clojure}}
Line 1,577:
(recur coll (pop stack))))
(zero? (count stack)))))</lang>
There are other ways to express the <code>balanced?</code> function.
* We can use <code>reduce</code> to consume the sequence:
:<lang Clojure>(defn balanced? [s]
(empty?
(reduce
(fn [stack first]
(case first
\[ (conj stack \[)
\] (if (seq stack)
(pop stack)
(reduced [:UNDERFLOW]))))
'()
s)))</lang>
* Only <code>[</code>s are put on the stack. We can just count the unmatched ones.
:<lang Clojure>(defn balanced? [s]
(let [opens-closes (->> s
(map {\[ 1, \] -1})
(reductions + 0))]
(and (not-any? neg? opens-closes) (zero? (last opens-closes))))) </lang>
Output:
Line 1,582 ⟶ 1,604:
<pre>user> (->> (range 10)
(map gen-brackets ,)
(map (juxt identity balanced?) ,
vec)
[["" true]
["[]" true]
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