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O(1) Max in Stack

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Problem

Ring doorbell firmware may need to track the largest pending priority while processing events. Design a stack that supports push, pop, and get_max in O(1) worst-case time per operation.

Implement max_stack_operations(operations). Each operation is represented as a list:

  • ["push", value] adds an integer to the top of the stack and produces no output.
  • ["pop"] removes and returns the top value.
  • ["get_max"] returns the largest value currently in the stack without removing it.

Return a list containing the results of every pop and get_max, in operation order. Inputs will never pop from an empty stack or call get_max on an empty stack. Duplicate values must be handled correctly. Do not use Python's max() during an operation, and do not scan the stack to answer get_max.

Formal Specification

Input: operations, a list of valid operation lists, where values are integers.

Output: A list of integers containing results from pop and get_max operations only.

Constraints

  • 1 <= len(operations) <= 200,000
  • -10^9 <= value <= 10^9
  • Every operation is valid for the current stack state
  • Each operation must run in O(1) worst-case time

Function Signature

def max_stack_operations(operations):
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