Easy Graphs Question 52 of 224

How do you count connected components in an undirected graph?

DSA interview set · Speak this in 60–90 seconds · Faridabad & Delhi NCR

IdeaGraphs

HowWhat happens inside

Why they askShows real use

Iterate vertices

Why interviewers care about Graphs:

This is a process

question about Graphs.

Panels listen for order,

trade-offs, and what you would actually do on a DSA project - not buzzwords.

Stay structured

Name the idea, why it exists, then one short example.

Close cleanly

End with when you use it and one common pitfall.

Before you speak the answer, walk the interviewer through these steps:

1
Define it
Iterate vertices
2
whenever you find an
unvisited one, run BFS or DFS to mark its whole component and increment the count.
3
Total time is O(V+E)
because each vertex and edge is processed once.
4
Union-Find is an alternative
with nearly O(V+E) after path compression.
5
Common mistake
What juniors usually get wrong.
6
Close
When you pick this over the alternative.

Here's a short line you can speak, broken into clear beats:

Say this line

“Total time is O(V+E) because each vertex and edge is processed once.”

Break into beats

TotaltimeisOVE

Speaking order

2987408337471632900

Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.

Iterate vertices whenever you find an unvisited one, run BFS or DFS to mark its whole component and increment the count.