26 sections · 205 pages
Name the pattern, copy the skeleton, change the knobs.
32 pattern guides, each opening with the copy-paste Java template for that pattern, followed by 153 worked problem walkthroughs with complexity analysis and the traps that come with them.
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The 22 patterns
Detailed index →In study order. Read section 0 first — the rest assume it.
- 00
Foundations
Big O, arrays, Java collections tips and tree fundamentals.
6 pages
- 01
Two Pointers
Sorted arrays and pair/triplet search.
6 pages
- 02
Sliding Window
Contiguous subarrays and substrings.
5 pages
- 03
Hashing & Frequency Maps
O(1) lookups and counting.
5 pages
- 04
Fast & Slow Pointers
Linked list cycles and finding the middle.
5 pages
- 05
Merge Intervals
Overlapping ranges.
5 pages
- 06
Cyclic Sort
Problems over a fixed 1..N range.
4 pages
- 07
Linked List Reversal
In-place pointer manipulation.
5 pages
- 08
BFS
Tree levels and shortest path on unweighted graphs.
6 pages
- 09
DFS
Tree paths and exhaustive search.
6 pages
- 10
Two Heaps
Running median and scheduling.
4 pages
- 11
Backtracking & Subsets
Combinations, permutations and subsets.
5 pages
- 12
Binary Search (Modified)
Searching a sorted or monotonic answer space.
6 pages
- 13
Top 'K' Elements
PriorityQueue and heap selection.
4 pages
- 14
Dynamic Programming
Optimisation over overlapping subproblems.
8 pages
- 15
Blind 75
The curated 75-problem interview list, grouped by category.
89 pages
- 16
Graph Patterns
BFS, DFS, topological sort, union-find, Dijkstra and Bellman-Ford.
8 pages
- 17
Union-Find (DSU)
Dynamic connectivity and grouping.
1 pages
- 18
Tries
Prefix search and autocomplete.
1 pages
- 19
Greedy
Sort-and-sweep and interval selection.
1 pages
- 20
Monotonic Stack
Next or previous greater/smaller element.
4 pages
- 21
Stacks & Queues
LIFO, FIFO, monotonic deque and design questions.
6 pages
Beyond the patterns
Start Here
Master roadmap, the all-21-templates cheat sheet, and the source references.
3 pages
MAANG Interview Prep
DSA lists, system design, LLD, Java/Spring, behavioural and healthcare-AI notes.
9 pages
Prompts
The AI prompt templates used to generate these pattern guides and problem write-ups.
2 pages
Practice Coding
Runnable standalone Java files, no Maven required.
1 pages