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If a queue is implemented using two stacks. In enqueue operation, all the elements are pushed from the first stack to the second stack. In dequeue operation pop an element from 1st stack.
Which of the following is/are true?
- a)Time complexity of enqueue is O(n).
- b)Time complexity of enqueue is O(1).
- c)Time complexity of dequeue is O(1).
- d)Time complexity of dequeue is O(n).
Correct answer is option 'A,C'. Can you explain this answer?
Most Upvoted Answer
If a queue is implemented using two stacks. In enqueue operation, all ...
Enqueue:
While 1st stack is not empty, push everything from 1st to 2nd stack.
Push an element to 1st stack.
Push everything back to 1st stack.
Here time complexity will be O(n).
Dequeue:
While 1st stack is not empty then Pop an item from stack 1 and return it. Here time complexity will be O(1).
Hence, the correct options are (A) and (C).
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If a queue is implemented using two stacks. In enqueue operation, all ...
Understanding Queue Implementation with Two Stacks
When implementing a queue using two stacks, the operations of enqueue and dequeue have different time complexities. Let's break down each operation:
Enqueue Operation
- In the enqueue operation, all elements from Stack 1 are transferred to Stack 2, which reverses their order.
- After transferring, a new element is pushed onto Stack 2.
- This results in a time complexity of O(n) for the enqueue operation, where n is the number of elements in Stack 1.
Dequeue Operation
- In the dequeue operation, we simply pop the top element from Stack 1.
- If Stack 1 is not empty, this operation takes constant time, O(1).
- If Stack 1 is empty, we need to transfer elements from Stack 2 back to Stack 1, which is still an O(n) operation but occurs only when Stack 1 is empty.
Summary of Time Complexities
- Enqueue: O(n) - All elements must be moved to Stack 2.
- Dequeue: O(1) - Directly pops from Stack 1 if it is not empty.
Conclusion
Therefore, the correct statements regarding the time complexities of the enqueue and dequeue operations are:
- a) Time complexity of enqueue is O(n). (True)
- c) Time complexity of dequeue is O(1). (True)
Thus, the correct answer is indeed options A and C.
When implementing a queue using two stacks, the operations of enqueue and dequeue have different time complexities. Let's break down each operation:
Enqueue Operation
- In the enqueue operation, all elements from Stack 1 are transferred to Stack 2, which reverses their order.
- After transferring, a new element is pushed onto Stack 2.
- This results in a time complexity of O(n) for the enqueue operation, where n is the number of elements in Stack 1.
Dequeue Operation
- In the dequeue operation, we simply pop the top element from Stack 1.
- If Stack 1 is not empty, this operation takes constant time, O(1).
- If Stack 1 is empty, we need to transfer elements from Stack 2 back to Stack 1, which is still an O(n) operation but occurs only when Stack 1 is empty.
Summary of Time Complexities
- Enqueue: O(n) - All elements must be moved to Stack 2.
- Dequeue: O(1) - Directly pops from Stack 1 if it is not empty.
Conclusion
Therefore, the correct statements regarding the time complexities of the enqueue and dequeue operations are:
- a) Time complexity of enqueue is O(n). (True)
- c) Time complexity of dequeue is O(1). (True)
Thus, the correct answer is indeed options A and C.
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If a queue is implemented using two stacks. In enqueue operation, all the elements are pushed from the first stack to the second stack. In dequeue operation pop an element from 1st stack.Which of the following is/are true?a)Time complexity of enqueue is O(n).b)Time complexity of enqueue is O(1).c)Time complexity of dequeue is O(1).d)Time complexity of dequeue is O(n).Correct answer is option 'A,C'. Can you explain this answer? for Computer Science Engineering (CSE) 2025 is part of Computer Science Engineering (CSE) preparation. The Question and answers have been prepared according to the Computer Science Engineering (CSE) exam syllabus. Information about If a queue is implemented using two stacks. In enqueue operation, all the elements are pushed from the first stack to the second stack. In dequeue operation pop an element from 1st stack.Which of the following is/are true?a)Time complexity of enqueue is O(n).b)Time complexity of enqueue is O(1).c)Time complexity of dequeue is O(1).d)Time complexity of dequeue is O(n).Correct answer is option 'A,C'. Can you explain this answer? covers all topics & solutions for Computer Science Engineering (CSE) 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for If a queue is implemented using two stacks. In enqueue operation, all the elements are pushed from the first stack to the second stack. In dequeue operation pop an element from 1st stack.Which of the following is/are true?a)Time complexity of enqueue is O(n).b)Time complexity of enqueue is O(1).c)Time complexity of dequeue is O(1).d)Time complexity of dequeue is O(n).Correct answer is option 'A,C'. Can you explain this answer?.
If a queue is implemented using two stacks. In enqueue operation, all the elements are pushed from the first stack to the second stack. In dequeue operation pop an element from 1st stack.Which of the following is/are true?a)Time complexity of enqueue is O(n).b)Time complexity of enqueue is O(1).c)Time complexity of dequeue is O(1).d)Time complexity of dequeue is O(n).Correct answer is option 'A,C'. Can you explain this answer? for Computer Science Engineering (CSE) 2025 is part of Computer Science Engineering (CSE) preparation. The Question and answers have been prepared according to the Computer Science Engineering (CSE) exam syllabus. Information about If a queue is implemented using two stacks. In enqueue operation, all the elements are pushed from the first stack to the second stack. In dequeue operation pop an element from 1st stack.Which of the following is/are true?a)Time complexity of enqueue is O(n).b)Time complexity of enqueue is O(1).c)Time complexity of dequeue is O(1).d)Time complexity of dequeue is O(n).Correct answer is option 'A,C'. Can you explain this answer? covers all topics & solutions for Computer Science Engineering (CSE) 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for If a queue is implemented using two stacks. In enqueue operation, all the elements are pushed from the first stack to the second stack. In dequeue operation pop an element from 1st stack.Which of the following is/are true?a)Time complexity of enqueue is O(n).b)Time complexity of enqueue is O(1).c)Time complexity of dequeue is O(1).d)Time complexity of dequeue is O(n).Correct answer is option 'A,C'. Can you explain this answer?.
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