Implement Deque with O(n) time
Last updated: September 23, 2025
Quick Overview
Implement a Deque (double-ended queue) data structure that supports the operations of adding and removing elements from both ends in O(n) time. Your implementation should include methods for adding elements to the front and back, removing elements from the front and back, and checking if the deque is empty. Ensure that your code handles edge cases, such as operations on an empty deque.
Expedia
September 23, 20251
8
4,257 solved
Implement a Deque (double-ended queue) data structure that supports the operations of adding and removing elements from both ends in O(n) time. Your implementation should include methods for adding elements to the front and back, removing elements from the front and back, and checking if the deque is empty. Ensure that your code handles edge cases, such as operations on an empty deque.
Expedia uses this problem in the Phone Screen to evaluate your algorithmic thinking. They expect you to discuss multiple approaches, analyze trade-offs between them, and implement the optimal solution with clean, readable code.
What the Interviewer Expects
- Identify the correct data structure and algorithm for the problem
- Write clean, bug-free code with proper variable naming
- Analyze time and space complexity correctly
- Handle basic edge cases (empty input, single element)
- Communicate your thought process while coding
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- What if the input doesn't fit in memory?
- Can you solve this in a single pass?
- How would you test this solution thoroughly?
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Practice DSA ProblemsSample Answer
Problem Analysis
The task is to implement a Deque (double-ended queue) that allows adding and removing elements from both ends efficiently. Given that the operations should be performed in O(n) time, a linked list is ...
Approach
- Define Node Class: Create a
Nodeclass that represents each element in the Deque, containingvalue,prev(pointer to the previous node), andnext(pointer to the next node). - **Define...
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