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LetsGit.IT/Categories/Algorithms
Algorithmshard

What is Dijkstra's Algorithm?

Tags
#graph#shortest-path#dijkstra#algorithm
Back to categoryPractice quiz

Answer

Dijkstra’s algorithm computes shortest paths from a single source in a graph with non‑negative edge weights. It repeatedly picks the closest unvisited node (usually via a priority queue) and relaxes outgoing edges, achieving O((V+E) log V) time with a heap.

Advanced answer

Deep dive

Expanding on the short answer — what usually matters in practice:

  • Context (tags): graph, shortest-path, dijkstra, algorithm
  • Complexity: compare typical operations (average vs worst-case).
  • Invariants: what must always hold for correctness.
  • When the choice is wrong: production symptoms (latency, GC, cache misses).
  • Explain the "why", not just the "what" (intuition + consequences).
  • Trade-offs: what you gain/lose (time, memory, complexity, risk).
  • Edge cases: empty inputs, large inputs, invalid inputs, concurrency.

Examples

A tiny example (an explanation template):

// Example: discuss trade-offs for "what-is-dijkstra's-algorithm?"
function explain() {
  // Start from the core idea:
  // Finds the shortest paths between nodes in a graph with non-negative edge weights using a p
}

Common pitfalls

  • Too generic: no concrete trade-offs or examples.
  • Mixing average-case and worst-case (e.g., complexity).
  • Ignoring constraints: memory, concurrency, network/disk costs.

Interview follow-ups

  • When would you choose an alternative and why?
  • What production issues show up and how do you diagnose them?
  • How would you test edge cases?

Related questions

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What does the Floyd–Warshall algorithm compute and what is its complexity?
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A* vs Dijkstra — what’s the difference and when is A* faster?
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Why doesn’t Dijkstra work with negative edge weights, and what can you use instead?
#dijkstra#bellman-ford#negative-weights
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What is a topological sort and when is it possible?
#topological-sort#dag#graph