Implement Stack with without recursion
Last updated: June 11, 2026
Quick Overview
Implement a stack data structure that supports the basic operations: push, pop, and peek, without using recursion. Your implementation should allow for adding and removing elements in a last-in, first-out (LIFO) manner. The stack should handle integer inputs and return the top element when peeked, or indicate if the stack is empty when attempting to pop or peek.
Scale AI
June 11, 202645
14
2,110 solved
Implement a stack data structure that supports the basic operations: push, pop, and peek, without using recursion. Your implementation should allow for adding and removing elements in a last-in, first-out (LIFO) manner. The stack should handle integer inputs and return the top element when peeked, or indicate if the stack is empty when attempting to pop or peek.
Scale AI uses this problem in the Onsite 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
- How would you parallelize this solution?
- What happens if the input contains duplicates?
- Can you optimize the space complexity of your solution?
- Can you solve this in a single pass?
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Practice DSA ProblemsSample Answer
Problem Analysis
To implement a stack without recursion, we need to consider how stacks operate based on the Last-In-First-Out (LIFO) principle. The operations we must support are push, pop, and peek. The use of...
Approach
- Data Structure: We'll use a Python list to store the stack elements. This allows us to dynamically grow the stack as we
pushelements. - Push Operation: When we push an element, we will...
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