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Graphs

4 lessonsAbout 24 minutesAdvanced

This part of the DSA Tutorial runs from Graphs and How to Represent Them through to Dijkstra's Algorithm. There are 4 lessons here, and working through them takes about 24 minutes at a steady pace.

It follows on from Tries, so finish that first if you have not already — the examples below assume you are comfortable with it.

Each lesson below says what it covers before you open it. Read them in order the first time; afterwards this page works as a index you can jump back into when you need to check one thing.

  1. 1Graphs and How to Represent ThemA graph is nodes connected by edges. Learn adjacency lists versus matrices in JavaScript, when each is right, and how to spot a graph problem that is not described as one.
  2. 2Graph Traversal: BFS and DFSBreadth-first search finds shortest paths; depth-first explores deeply. Learn both in JavaScript, why every graph traversal needs a visited set, and how to choose between them.
  3. 3Topological SortTopological sort orders tasks so every dependency comes first. Learn Kahn's algorithm in JavaScript, how it detects impossible cycles, and where build tools use it.
  4. 4Dijkstra's AlgorithmDijkstra finds the cheapest path when edges have weights, where BFS only finds the fewest edges. Learn the implementation in JavaScript with a priority queue, and why negative weights break it.
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