Implement Deque with in-place
Last updated: February 2, 2026
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 adding and removing elements from the front and back, as well as checking if the deque is empty. The input will consist of a series of operations to perform on the deque, and the output should reflect the state of the deque after each operation.
SentinelOne
February 2, 202623
11
1,006 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 adding and removing elements from the front and back, as well as checking if the deque is empty. The input will consist of a series of operations to perform on the deque, and the output should reflect the state of the deque after each operation.
This coding problem is frequently asked during Take-home Project at SentinelOne. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. SentinelOne expects candidates to write production-quality code, not just solve the puzzle.
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 modify your solution to handle streaming input?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to implement a Deque (double-ended queue) that allows insertion and removal of elements from both ends in O(1) time. The appropriate data structure for this implementation is a...
Approach
To implement the deque, we will use a doubly linked list. Each node will contain a value and pointers to both the previous and next nodes.
- Node Structure: Define a
Nodeclass with attributes...
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