Lesson overview · Free interview practice

Graph DFS

Explore graphs using Depth-First Search.

Topics in the full lesson
  • Concept and Use Cases
  • When to Use
  • Time and Space Complexity
  • Graph DFS for Detecting Cycles
  • Finding Connected Components in an Undirected Graph
  • Topological Sorting of a Directed Acyclic Graph (DAG)
  • Finding All Paths Between Two Vertices

Practice Problems

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Number of Connected Components in an Undirected Graph

Question

Given n nodes labeled 0..n-1 and a list of undirected edges, return the number of connected components in the resulting graph.

Take a moment to think about this before revealing the answer

Explain your reasoning or try an implementation before comparing answers.

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Course Schedule

Question

There are numCourses courses labeled 0..numCourses-1. Given a list of prerequisites where prerequisites[i] = [a, b] means "to take course a you must first complete course b", return true if you can finish all courses (no cycle in the prerequisite graph), otherwise false.

Take a moment to think about this before revealing the answer

Explain your reasoning or try an implementation before comparing answers.

Practice on LeetCode
CodingMedium

Graph Valid Tree

Question

You are given n nodes labeled 0..n-1 and a list of edges (undirected). Return true if these edges form a valid tree — that is, the graph is connected and contains no cycles.

Take a moment to think about this before revealing the answer

Explain your reasoning or try an implementation before comparing answers.

Practice on LeetCode

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