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Validate Stack Sequences

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Linda Zhou edited this page Nov 2, 2022 · 8 revisions

Problem Highlights

  • 🔗 Leetcode Link: Validate Stack Sequences
  • 💡 Problem Difficulty: Medium
  • ⏰ Time to complete: __ mins
  • 🛠️ Topics: Array, Stack
  • 🗒️ Similar Questions:

1: U-nderstand

Understand what the interviewer is asking for by using test cases and questions about the problem.

  • Established a set (2-3) of test cases to verify their own solution later.
  • Established a set (1-2) of edge cases to verify their solution handles complexities.
  • Have fully understood the problem and have no clarifying questions.
  • Have you verified any Time/Space Constraints for this problem?
  • We have to push the items in order, so when do we pop them?
    • If the stack has say, 2 at the top, then if we have to pop that value next, we must do it now. That's because any subsequent push will make the top of the stack different from 2, and we will never be able to pop again.

Run through a set of example cases:



2: M-atch




Match what this problem looks like to known categories of problems, e.g. Linked List or Dynamic Programming, and strategies or patterns in those categories.




    

  • Stack: What could we push onto a stack to make this problem easier? Stacks don’t allow us to keep track of data based on keys.
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  • Queue: Queues fall into the same category as Stacks, do we need to maintain any sense of ordering to solve this problem?
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  • HashMap: HashMaps allow us to store data for quick access. What could we store in a HashMap to make this problem easier?
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  • Heap: Do we need some sort of ordering to our data that a Heap could provide?
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3: P-lan




Plan the solution with appropriate visualizations and pseudocode.




General Idea:




⚠️ Common Mistakes


    

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4: I-mplement




Implement the code to solve the algorithm.








5: R-eview




Review the code by running specific example(s) and recording values (watchlist) of your code's variables along the way.




    

  • Trace through your code with an input to check for the expected output
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  • Catch possible edge cases and off-by-one errors
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6: E-valuate




Evaluate the performance of your algorithm and state any strong/weak or future potential work.




    

  • 
Time Complexity:
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Space Complexity:
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