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šŸ§®

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DSA

Patterns over solutions. Learn the 10ā€“15 core patterns and you can solve most interview problems from first principles.

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Complexity reference

O(1)ConstantHash map lookup, array access
O(log n)LogarithmicBinary search, balanced BST
O(n)LinearLinear scan, single loop
O(n log n)LinearithmicMerge sort, heap sort
O(nĀ²)QuadraticBubble sort, nested loops
O(2āæ)ExponentialRecursive subsets, brute force

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Core patterns

Arrays & Strings

Two pointers, sliding window, prefix sum.

Linked Lists

Fast/slow pointers, reversal, cycle detection.

Trees & Graphs

BFS, DFS, binary trees, BST, graph traversals.

Sorting & Searching

Common sorts, binary search, and variations.

Dynamic Programming

Memoization, tabulation, common DP patterns.
ā—† Pattern Recognition
Before writing code, identify the pattern. Two pointers? Sliding window? BFS/DFS? DP? Picking the right pattern is 80% of the solution.
šŸ’” Interview Tip
Always state the brute force solution first, then optimize. It shows you understand the problem before jumping to complex solutions. Interviewers prefer a working O(nĀ²) over a broken O(n log n).