Month 2 — Patterns Mastery

Theme: Stop solving problems case-by-case. Start recognizing the pattern, then dispatching the right template. Weeks 5–8 trade depth on individual data structures for breadth of patterns — graphs, two-pointers, sliding windows, monotonic stacks, intervals, backtracking, trie, two-heaps. By month’s end, you should be able to look at a problem statement and call out the pattern name within 30 seconds.

Weekly breakdown

  • Week 5 — Graphs Intro: BFS, DFS, and the Topological Mindset (README) Number of Islands · Clone Graph · Course Schedule · Pacific Atlantic · Word Ladder

  • Week 6 — Two Pointers, Sliding Window, Prefix Sums (planned)

  • Week 7 — Monotonic Stacks, Intervals, Greedy (planned)

  • Week 8 — Backtracking, Trie, Two Heaps (planned)

Milestones

By end of Month 2:

  • Recognize the 8 core algorithmic patterns from problem statement alone (BFS/DFS, two-pointer, sliding window, prefix sum, monotonic stack, interval-sort, backtracking, two-heap)
  • Write canonical BFS / DFS / topo sort / multi-source BFS templates from memory
  • Solve LC Medium graph + sliding-window problems in 25 minutes
  • Articulate when each pattern applies AND when it doesn’t (the “negative space” matters as much)

Required cross-references

  • phase-04-graphs/labs/ — every Week 5 problem cross-references a lab here
  • phase-02-patterns/labs/lab-01-two-pointers.md — Week 6 base reading
  • FRAMEWORK.md — every problem walks the 9-step framework
  • SPACED_REPETITION.md — re-solve schedule for prior weeks during this month