There was no way I was figuring out that lower ASCII value equals optimal deletion without a hint.
First, clarify the problem statement and constraints, especially the role of ASCII values in deletion decisions. Then, propose a greedy strategy that processes characters in a specific order (e.g., ascending ASCII) and prove its optimality using an exchange argument. Finally, analyze time and space complexity and discuss potential edge cases.
Pro tip: At AWS, interviewers value scalability and correctness. Explicitly state the greedy choice and prove it with an exchange argument, then mention how your solution handles large inputs efficiently.
Ask questions to confirm the exact deletion rule, input format, and constraints. Ensure you understand how ASCII values influence the deletion order.
Determine the locally optimal decision at each step, such as deleting the character with the smallest ASCII value that satisfies the condition. Explain why this leads to a global optimum.
Use an exchange argument to show that any optimal solution can be transformed into the greedy solution without worsening the result. This demonstrates the correctness of the greedy approach.
Derive the time and space complexity of your algorithm, considering sorting or heap operations if needed. Discuss how it scales with input size.
Test with small inputs, all characters deletable, no characters deletable, and duplicate ASCII values. Ensure your solution handles these gracefully.
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