Implement Deque with in-place
Last updated: July 3, 2025
Quick Overview
Implement a deque (double-ended queue) data structure that supports in-place operations for adding and removing elements from both ends in O(1) time. Your implementation should include methods for inserting and deleting elements at the front and back, as well as retrieving elements from both ends. Ensure that your solution efficiently handles edge cases, such as operations on an empty deque.
Shopify
July 3, 2025104
6
4,800 solved
Implement a deque (double-ended queue) data structure that supports in-place operations for adding and removing elements from both ends in O(1) time. Your implementation should include methods for inserting and deleting elements at the front and back, as well as retrieving elements from both ends. Ensure that your solution efficiently handles edge cases, such as operations on an empty deque.
This coding problem is frequently asked during Onsite at Shopify. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Shopify expects candidates to write production-quality code, not just solve the puzzle.
What the Interviewer Expects
- Quickly identify the optimal approach and its theoretical basis
- Handle complex algorithm design with multiple interacting components
- Write concise, elegant code under time pressure
- Prove correctness of your approach and discuss alternative solutions
- Optimize beyond the obvious: discuss constant factor improvements
- Address follow-up variations and explain how the solution generalizes
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
- How would you modify your solution to handle streaming input?
- What happens if the input contains duplicates?
- How would your solution change if the input was sorted?
- What if the input doesn't fit in memory?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires implementing a double-ended queue (deque) that supports in-place operations for adding and removing elements from both ends in O(1) time. This suggests a need for a circular buffe...
Approach
- Define a Node class to represent each element in the deque, containing data, a reference to the next node, and a reference to the previous node.
- Define a Deque class with properties for the fron...
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