About This Pattern
Master the Hash Set pattern by practicing these problems organized by difficulty.Focus on the Key Signals - these are the indicators that tell you when to use this pattern.
Easy (1)
Contains Duplicate
Given an integer array, return true if any value appears at least twice in the array.
Key Signals:
Check for existenceUniqueness validationNo ordering needed
Medium (1)
Longest Consecutive Sequence
Find the length of the longest consecutive elements sequence in O(n) time.
Key Signals:
Find sequence startO(n) requiredCheck neighbors