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Leetcode
Medium
Hash Maps
Design
Google
Counter
Design a counter that supports updating counts for string keys and querying them efficiently.
Acceptance 0%
Problem Statement
Problem
Implement a counter data structure that stores integer counts for string keys.
Support operations to:
- increase the count for a key by 1
- decrease the count for a key by 1, removing the key if its count becomes 0
- return the current count for a key
The counter should behave like a mutable in-memory frequency table.
Notes
- If a key does not exist, its count is considered 0.
- Decrementing a missing key should have no effect.
- All operations should be efficient.
Input Format
A sequence of operations on a counter object, each operating on a string key.
Output Format
Return the result of each query operation, and keep internal state updated after each modification.
Constraints
- Keys are non-empty strings.
- Counts are integers and never negative.
- Operations should be near O(1) on average.
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