Following is an incorrect pseudocode for the algorithm which is supposed to determine whether a sequence of parentheses is balanced:
C
declare a character stack while ( more input is available)
{ read a character
if ( the character is a \'(\' )
push it on the stack
else if ( the character is a \')\' and the stack is not empty )
pop a character off the stack
else
print \"unbalanced\" and exit
}
print \"balanced\"
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Which of these unbalanced sequences does the above code think is balanced?
(A)
((())
(B)
())(()
(C)
(()()))
(D)
(()))()
Answer: (A)
Explanation:
At the end of while loop, we must check whether the stack is empty or not. For input ((()), the stack doesn\’t remain empty after the loop. See http://www.geeksforgeeks.org/check-for-balanced-parentheses-in-an-expression/amp/ for details.
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