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Placement fast track
What to do, and what to skip
Short on time before campus OAs and interviews? Of the 99 subpatterns in the DSA patterns sheet, 41 carry most of the interview weight. Do those first (76 problems below), 18 more if you have time, and skip the other 40 until after your OAs.
- Read the pattern guide for each "Must do" subpattern, then solve its problems without looking at the editorial first.
- Stuck for 20 minutes? Open the hints on the problem page one at a time before you read the editorial.
- Once the must-dos of a pattern are done, take a timed OA set to check you can do it under the clock.
- Only then go back for "If you have time". Leave "Skip for now" until after your OAs.
The 13 interview-soon patterns
Two Pointers4 must do · 7 of 7 kept · ~3 h
- Happy NumberEasy
- Find the Duplicate NumberMedium
- Squares of a Sorted ArrayEasy
- 3SumMedium
- Must doIn-place Array Modification
- If you have timeString Comparison with Backspaces
- If you have timeString Reversal
- Reverse StringEasy
- If you have timeFixed Separation (Nth Node from End)
Sliding Window2 must do · 3 of 4 kept · ~2.5 h
- If you have timeCharacter Frequency Matching
- Permutation in StringMedium
- Skip for nowMonotonic Queue for Max/Min
Binary Search Patterns3 must do · 3 of 5 kept · ~2.5 h
- Must doOn Sorted Array/List
- Must doFind First/Last Occurrence
- Skip for nowMedian and Kth of Two Sorted Arrays
- Skip for nowOn Answer / Condition Function
Array/Matrix Manipulation Patterns5 must do · 6 of 10 kept · ~4 h
- Must doSpiral Traversal
- Spiral MatrixMedium
- Spiral Matrix IVMedium
- Set Matrix ZeroesMedium
- Game of LifeMedium
- Two SumEasy
- Group AnagramsMedium
- If you have timeProduct Except Self (Prefix/Suffix Products)
- Skip for nowPlus One (Handling Carry)
- Skip for nowArray - Cyclic Sort
- Skip for nowHashing - Previously Seen / Existence Check
- Skip for nowIn-place Rotation
Linked List Manipulation Patterns2 must do · 3 of 5 kept · ~2 h
- Must doIn-place Reversal
- Must doMerging Two Sorted Lists
- If you have timeReordering / Partitioning
- Rotate ListMedium
- Skip for nowAddition of Numbers
- Skip for nowIntersection Detection
Stack Patterns2 must do · 3 of 6 kept · ~2.5 h
- Must doValid Parentheses Matching
- Must doMonotonic Stack
- If you have timeLargest Rectangle in Histogram
- Skip for nowStack - Min Stack Design
- Skip for nowSimulation / Backtracking Helper
- Skip for nowExpression Evaluation (RPN/Infix)
String Manipulation Patterns2 must do · 3 of 6 kept · ~2 h
- If you have timeRepeated Substring Pattern Detection
- Skip for nowNaive / KMP / Rabin-Karp
- Skip for nowInteger and Roman Conversion
- Skip for nowMultiply Strings (Manual Simulation)
Tree Traversal Patterns (DFS & BFS)4 must do · 4 of 6 kept · ~3 h
- Must doRecursive Preorder Traversal
- Must doRecursive Inorder Traversal
- Must doLevel Order Traversal
- Skip for nowRecursive Postorder Traversal
- Skip for nowSerialization and Deserialization
Heap (Priority Queue) Patterns2 must do · 3 of 4 kept · ~2 h
- Must doK-way Merge
- If you have timeTwo Heaps for Median Finding
Greedy Patterns2 must do · 4 of 7 kept · ~3 h
- Jump Game IIMedium
- Jump GameMedium
- Must doInterval Merging/Scheduling
- If you have timeSorting Based
- If you have timeBuy/Sell Stock
- Skip for nowTask Scheduling (Frequency Based)
- Skip for nowLine Sweep
- Skip for nowGas Station Circuit
Backtracking Patterns4 must do · 6 of 7 kept · ~3 h
- Must doSubsets (Include/Exclude)
- Must doPermutations
- PermutationsMedium
- Next PermutationMedium
- Must doCombination Sum
- Combination SumMedium
- Combination Sum IIMedium
- If you have timeN-Queens / Constraint Satisfaction
- Sudoku SolverHard
- If you have timeParentheses Generation
- Generate ParenthesesMedium
- Skip for nowPalindrome Partitioning
Dynamic Programming (DP) Patterns6 must do · 9 of 12 kept · ~5 h
- Must do1D Array (Fibonacci Style)
- Climbing StairsEasy
- House Robber IIMedium
- Maximum SubarrayMedium
- Maximum Sum Circular SubarrayMedium
- Target SumMedium
- Partition Equal Subset SumMedium
- Coin ChangeMedium
- Coin Change IIMedium
- If you have time1D Array (Word Break Style)
- Word Break IIHard
- TriangleMedium
- Unique Paths IIMedium
- If you have time2D Array (Edit Distance / Levenshtein Distance)
- If you have timeLongest Increasing Subsequence (LIS)
- Skip for nowStock problems
- Skip for nowCatalan Numbers
- Skip for nowInterval DP
Graph Traversal Patterns (DFS & BFS)3 must do · 5 of 12 kept · ~5 h
- Flood FillEasy
- Max Area of IslandMedium
- 01 MatrixMedium
- Word LadderHard
- Parallel Courses IIIHard
- Minimum Height TreesMedium
- If you have timeGraph DFS - Cycle Detection (Directed Graph)
- If you have timeDeep Copy / Cloning
- Clone GraphMedium
- Skip for nowShortest Path (Dijkstra's Algorithm)
- Skip for nowShortest Path (Bellman-Ford / BFS+K)
- Skip for nowUnion-Find (Disjoint Set Union - DSU)
- Skip for nowBridges & Articulation Points (Tarjan low-link)
Skip for now: the deep-dive patterns
Bit Manipulation Patterns, Design Patterns, Segment Tree & Fenwick Tree Patterns. The sheet tags them deep-dive: learn them after the patterns above. The same goes for every subpattern marked "Skip for now".
Check yourself under the clock
Timed OA sets graded on hidden tests, with a score report. Two sets are free.
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