Toolbox: free-recall review
Free-recall prompts on technique selection across the algorithms track — reconstruct the decision tree from constraints and problem shape to the right tool.
Pattern recognition sticks only when you can produce the decision tree from memory under pressure. For each prompt, say or write the full reasoning — from the clue in the problem to the technique and its cost — before you reveal the model answer.
Reconstruct the track’s selection logic without looking back: how to read constraints into a complexity budget, which problem verbs map to which technique family, and why the tempting alternative is the trap.
- 01How do you turn the input-size constraint into a complexity budget before choosing a technique?
- 02Map each problem verb to its technique family: 'does X exist / count distinct', 'k-th smallest / next by priority', 'count ways or optimise over overlapping subproblems', 'best local pick you can justify'.
- 03When sorted input appears, which two techniques does it unlock, and how do you pick between them?
- 04Distinguish when a graph problem needs BFS, Dijkstra, topological sort, or Union-Find.
- 05Why is recognising overlapping subproblems the pivotal moment in problem solving, and what are your three responses to it?
- 06Give the full top-of-tree decision flow you run on a brand-new problem.
If you could reconstruct each answer cold, you hold the track’s spine: constraints become a complexity budget, the problem’s verb names the technique family, sorted input unlocks binary search or two pointers, the graph variant picks BFS / Dijkstra / toposort / Union-Find, and spotting overlapping subproblems is the pivot from exponential to polynomial. The toolbox is one decision flow run fast — budget, verb, structure, subproblem check, data structure, sanity check — not a pile of memorised algorithms.
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