DSA topic · Stage 7

Greedy interview preparation

Make a locally optimal choice only when an exchange or invariant argument supports it.

DSA prep Practice 2 questions

Concept

Greedy problems test proof, not simply choosing the largest or smallest visible item.

Complexity lens

Often sorting dominates; explain why revisiting an earlier choice is unnecessary.

Common mistakes

Using greedy without justification
Choosing the wrong ordering key
Confusing greedy with dynamic programming

Recognition

Decide from constraints, not labels.

These clues narrow the model. They do not replace an invariant or complexity check.

Recognition clues

A locally best boundary leaves maximal room for the future
An exchange argument can replace an arbitrary optimal choice
Past choices never need revision once the invariant is proved

Implementation options

Sort by finish, start, cost, or gain according to the proof
Single-pass boundary maintenance
Heap-assisted greedy when candidates become available over time

Interview behavior

Offer the correctness argument before code
Identify the counterexample that defeats a tempting alternative
Separate the greedy choice from the data structure used to obtain it

Patterns that operate on this topic

Merge IntervalsThe output prefix is fully merged and nonoverlapping; the current interval covers every processed input not already emitted.GreedyAfter each choice, there exists an optimal completion consistent with every choice made so far.

Representative problems

2 current Greedy questions.

Exact active distribution: 0 easy, 2 medium, 0 hard. External records contain metadata and original guidance only.

External catalogUnverified
Minimum Number of Arrows to Burst Balloons
Provides a public interval-scheduling variation without requiring a premium Meeting Rooms problem.
Sorting Intervals Greedy Merge Intervals
MediumFree / publicSolve problem
External catalogUnverified
Jump Game
Requires a crisp invariant for why the farthest reachable point is sufficient.
Greedy Greedy
MediumFree / publicSolve problem

Review state

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Question pages let you record local completion. Account status, confidence, notes, and a topic roll-up are shown only when private account persistence is available.

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Review prompts

What exchange proves this choice safe?
Which sort key does the proof require?
Would future information force a revised choice?

Prerequisites and next step

Mix the patterns

Use an unlabeled set to test transfer after the topic-specific set.

Build a mixed set

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Greedy interview preparation

Decide from constraints, not labels.

Recognition clues

Implementation options

Interview behavior

Patterns that operate on this topic

2 current Greedy questions.

Minimum Number of Arrows to Burst Balloons

Jump Game

Sign in for private topic progress

Mix the patterns

Greedy interview preparation

Decide from constraints, not labels.

Recognition clues

Implementation options

Interview behavior

Patterns that operate on this topic

2 current Greedy questions.

Minimum Number of Arrows to Burst Balloons

Jump Game

Sign in for private topic progress

Mix the patterns