A stack can be implemented using two queues. Let stack to be implemented be ‘x’ and queues used to implement be ‘a’ and ‘b’.
Method 1 (By push operation)
This method makes sure that the newly entered element is always at the front of ‘a’, so that pop operation just dequeues from ‘a’. ‘b’ is used to put every new element at front of ‘b’.
Method 2 (By making pop operation costly)
In a push operation, the new element is always enqueued to a. In pop() operation, if b is empty then all the elements except the last, are moved to b. Finally, the last element is dequeued from a and returned.
Therefore Option 2 is correct
The Preorder traversal of a tree given below is:
The correct solution is 'option 1'.
Key Points
Algo Preorder(tree root)
{
}
Thus, the correct answer is: A B D F E C G I H J K L
Additional Information
Tree traversal | ||||||
Method flow |
Inorder | preorder | postorder |
Converse Inorder |
Converse Preorder | Converse Postorder |
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Concept:
Explanation:
A recursive problem like the Tower of Hanoi can be rewritten using system stack or user-defined stack
Recurrence relation of tower of Hanoi: T(n) = 2T(n - 1) + 1
Additional Information
Number of moves required for n disc in a Tower of Hanoi is 2n – 1 = 27 – 1 = 127.
Stack underflow happens when one tries to pop (remove) an item from the stack when nothing is actually there to remove.
Total MCQS : 128
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gradeTotal MCQS : 133
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gradeTotal MCQS : 165
gradeTotal MCQS : 61
gradeTotal MCQS : 133
gradeTotal MCQS : 120
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gradeTotal MCQS : 36
gradeTotal MCQS : 7
gradeTotal MCQS : 175
gradeTotal MCQS : 2533
gradeTotal MCQS : 9
gradeTotal MCQS : 11
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