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Liam's Learning Path

Everything we have covered, in the order we covered it. Each lesson links to the pages that explain it, and to the problem set that practised it.

Timeline

Date Lesson What we covered Read Problem set
01-11 STL containers Pointers and references, vector / stack / queue / deque, vector as a stack, empty() STL Containers 1-vector_sort (5/11)
02-01 sort, iterators, custom sorting Math symbols, sort / swap / reverse on [begin, end), iterators, comparator functions Sorting & Comparators 1-vector_sort (5/11)
02-08 Comparators, struct, Big-O String concatenation, the cmp rule "should x come before y?", struct, growth of complexities Sorting & Comparators
Complexity & Constraints		 2-custom_sorting (2/4)
03-01 std::set (problem set 3) Unique sorted elements, iteration, begin / prev(end), find and erase; date taken from the problem set's submissions std::set 3-set (2/2)
03-08 Bitmask enumeration, fast power Enumerating all 2^n choices with state >> i & 1, spotting patterns and cycles in huge inputs Bitmasks & Bit Operations
Fast Power & Modulo		 4-quick_power (3/4)
03-18 USACO 2026 Contest 3 review Full solve of Contest 3; time-complexity table for a 1-second limit Complexity & Constraints
USACO 2026		 —
03-22 Purchasing Milk, bit operations CLion templates and Reformat Code; powers-of-two deals; shifts, AND, OR, XOR; sum constraints over test cases Bitmasks & Bit Operations
Complexity & Constraints
USACO 2026		 —
03-29 Make it work, make it fast Brute force first, then only update affected rectangles; size() is unsigned and wraps around Integer Types & Overflow
USACO 2026		 —
04-01 Replacement updates Remove the old contribution, update, add the new one: delta = new - old USACO 2026 —
04-05 USACO 2026 Contest 1; binary search Corner cases in Contest 1; the l <= r template that always prints ans Binary Search
USACO 2026		 5-BinarySearch (2/9)
04-12 Prefix sums + binary search pre[r] - pre[l-1]; largest valid r for each l; lambdas and captures Prefix Sum
Binary Search		 5-BinarySearch (2/9)
04-15 Binary search vs two pointers When each applies; the commented two-pointer template Binary Search
Two Pointers & Sliding Window		 5-BinarySearch (2/9)
04-29 Two pointers practice Prepend and Append, Balanced Team, Ternary String, Blinds (worked in class) Two Pointers & Sliding Window 6-TwoPointers (6/7)
05-10 Two pointers as add / del / check Templatising the window; longest sum <= 100 and shortest sum >= 100; greedy set assigned Two Pointers & Sliding Window
Greedy		 6-TwoPointers (6/7)
7-Greedy (9/10)
05-13 What is a graph Vertices, edges, reading an edge list, finding the neighbours of one vertex Graph Basics —
05-27 Adjacency matrix and list n^2 vs 2m numbers, neighbourhood, degree, sum of degrees = 2m Graph Basics —
06-08 Directed graphs In-degree and out-degree; OJ contest Graph Basics (P1201-P1204) Graph Basics —
07-23 AIO 2025 Q4, Q5; AIO 2024 Q6 ORAC: training first, the mountain, binary search; Pairing Cards; Twin Rivers AIO 2025
AIO 2024		 —
07-27 AIO 2025 Q5, Q6 Pairing Cards from both ends; Robot Writing layers AIO 2025 —
07-30 AIO 2025 Q6 proof; AIO 2024 practice Robot Writing claims 1-13; Javelin, Subbookkeeper, Shopping Spree, Backpacking, Tennis Robot II AIO 2025
AIO 2024		 —
08-05 AIO 2023 and AIO 2024 TeleTrip, Distincto's Raffle, Making Bank, Shoptimality, Wheeling and Dealing, Lights; AIO 2024 set AIO 2023
AIO 2024		 —
08-10 DP quick start; AIO 2022 State / transition / base / order / answer; Fibonacci, stairs, LIS; Composing Pyramids DP Quick Start
AIO 2022		 —
08-15 AIO 2021 Robot Vacuum, Art Class II, Melody, Social Distancing, Space Mission, Laser Cutter AIO 2021 —
08-19 AIO 2020 Baubles, Cookies, Ghost Encounters, Tennis Robot, Ladybugs II, Beach Umbrellas AIO 2020
Binary Search		 —
08-22 AIO 2019 Vases, RPS, Hiring Monks, Medusa's Snakes, Evading Capture (parity BFS), Lollipops II AIO 2019
BFS with Parity States		 —
08-23 DSU; AIO 2018 and 2025 Parent array, find with path compression, union; Street Construction to Detective; AIO 2025 set Disjoint Set Union
AIO 2018
AIO 2025		 —
09-12 AIO 2026 Jump on Platforms, IGM, Discount Destinations, Sunday Drive II, Prime Minister, Mundane Square AIO 2026 —
09-13 Graph review homework Problem set 8: Badge (follow the edges), Forever Winter (degrees), Ice Skating (build the graph, count components) Graph Basics
Disjoint Set Union		 8-Graph (0/3)

Topics by area

Problem sets

Dates come from submission history.

# Set Period Solved Avg. Rating
1 1-vector_sort 2026-01-31 ~ 2026-02-08 5/11 945
2 2-custom_sorting 2026-02-15 ~ 2026-02-19 2/4 850
3 3-set 2026-03-01 ~ 2026-03-01 2/2 900
4 4-quick_power 2026-03-05 ~ 2026-03-08 3/4 1225
5 5-BinarySearch 2026-04-16 ~ 2026-04-23 2/9 1144
6 6-TwoPointers 2026-05-03 ~ 2026-05-14 6/7 1271
7 7-Greedy 2026-05-10 ~ 2026-06-03 9/10 920
8 8-Graph — ~ — 0/3 1167

8 problem sets, 50 problems, 29 solved.

Contests

Credits & licenses

This is a free, non-commercial study resource made from Liam's lessons. Explanations, worked examples and AIO write-ups are ours; lesson notes and in-class code are reproduced unchanged. Problem statements are summarised in our own words and link to the originals on Codeforces, ORAC and USACO. Where a page borrows an idea or a figure from OI Wiki (CC BY-SA 4.0) or USACO Guide (CC BY-NC-SA 4.0), its own credits box says exactly what and from whom.