Cheat Sheet

Arrays & Hashing Cheat Sheet

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What is Arrays & Hashing?

Master the fundamentals of arrays and hash-based data structures for O(1) lookups.

Trigger Words

When you see these in a problem, think Arrays & Hashing:

contains duplicate arrays-and-hashing valid anagram two sum group anagrams top k frequent elements product of array except self valid sudoku longest consecutive sequence

Template Code

def containsDuplicate(nums: List[int]) -> bool:
    seen = set()
    for num in nums:
        if num in seen:
            return True
        seen.add(num)
    return False

Complexity

Typical Time	`O(n)`
Typical Space	`O(n)`

Common Variations

Basic Arrays & Hashing
Arrays & Hashing with constraints
Optimized Arrays & Hashing

Practice Problems

Contains Duplicate easy Valid Anagram easy Two Sum easy Group Anagrams easy Top K Frequent Elements easy

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Practice Arrays & Hashing

Learn to recognize patterns instantly with interactive MCQs.

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