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Week 07 — Jul 6–12, 2026 — Graphs (BFS/DFS)

Week 07 (Jul 6 – Jul 12, 2026) — GRAPHS (BFS/DFS) (Sprint S3 of 8)

Heaviest DSA week (13). Timer on, solo, no peek till timer expires.

→ Curriculum: [[Coach/project_dsa_sd_curriculum]] | Coach state: [[synthesis/Coach Hub]]

Goals This Week

13 DSA problems on time, solo
SD problem: URL Shortener (carried from S1) — base62, KGS, cache, hot-key
SD problem: Unique ID Generator in distributed systems — Snowflake (timestamp+machine+seq), UUID, ticket server, clock skew
Redis: Sorted sets (leaderboard, feed cache)
DDIA: Ch7 Sharding pt1
Sun Jul 12 scorecard + S4 direction

DSA Problem Set (13)

#	Problem	LC	Diff	Target	Solved?	Time	Notes
1	Number of Islands	200	M	20 min	☐		grid DFS/BFS flood fill
2	Max Area of Island	695	M	20 min	☐
3	Clone Graph	133	M	25 min	☐		hashmap old→new
4	Walls and Gates	286	M	25 min	☐		multi-source BFS
5	Rotting Oranges	994	M	25 min	☐		multi-source BFS + time
6	Pacific Atlantic Water Flow	417	M	30 min	☐		reverse DFS from oceans
7	Surrounded Regions	130	M	30 min	☐		border DFS guard
8	Course Schedule	207	M	30 min	☐		cycle detect / topo
9	Course Schedule II	210	M	30 min	☐		topo order (Kahn)
10	Graph Valid Tree	261	M	25 min	☐		union-find / connected+no cycle
11	Number of Connected Components	323	M	25 min	☐		union-find
12	Redundant Connection	684	M	30 min	☐		union-find detect
13	Word Ladder	127	H	40 min	☐		BFS shortest transform

Score: __/13 on time

SD + Redis + DDIA

Item	Status	Notes
SD: URL Shortener	⬜	base62 encode, KGS vs counter vs hash, 301 vs 302, cache-aside, hot-key math, storage sizing
SD: Unique ID Generator (distributed)	⬜	Snowflake (41b time + 10b machine + 12b seq), UUID vs Snowflake, ticket server, clock-skew handling
Redis: sorted sets	⬜	`ZADD`/`ZRANGE`/`ZREVRANGE`; leaderboard + timeline cache
DDIA: Ch7 Sharding pt1	⬜	range vs hash partitioning; secondary indexes

Daily Plan (compact)

Mon: graph theory refresh + LC 200, 695
Tue: LC 133, 286, 994
Wed: LC 417, 130 + Redis sorted sets
Thu: LC 207, 210 + SD Feed high-level
Fri: LC 261, 323, 684 + DDIA Ch7.1
Sat: LC 127 (hard) + Twitter Feed whiteboard
Sun: retro + scorecard + create S4 tracker

Decision Gate (Sun Jul 12)

Score	Verdict	S4
10–13	Pass strong	Adv Graphs + Greedy + WhatsApp
7–9	Patchy	Adv Graphs + retry weak graphs
<7	Fail	Repeat graphs core in S4

Hours Log

Day	Planned	Actual
Mon–Sun	~26h

Retro (fill Sun)

Solved on time: __/13 | Weakest: __ | SD: __ | Redis: __ | DDIA: __ | S4 decision: __