The famous list posted on Blind: a compact set of problems chosen so that solving all of them touches every pattern that shows up in interviews. Work through it topic by topic; each section builds intuition the next one reuses. Adapted to the problems available in the Solvarch catalog.
Hash maps, prefix products, and the classic buy/sell scan.
The canonical hash-map warm-up.
Kadane's algorithm — know it cold.
Hash set gives O(n) — sorting is the trap.
Window and pointer techniques over strings.
The hardest sliding window on the list.
Pointer surgery: reverse, detect, merge, rewire.
Recursion on trees, BST properties, and prefix trees.
The classic hard tree question.
BFS/DFS, topological sort, and union-find.
1-D and 2-D DP — the section people skip and regret.
The gateway DP.