Graphs

Question 1

How do you represent a graph with an adjacency list?

Answer 1

Use a mapping where each node points to a list of its neighbors.

Question 2

What’s an adjacency matrix?

Answer 2

A 2D grid where each cell shows whether an edge exists between nodes.

Question 3

What’s the difference between a directed and undirected graph?

Answer 3

Directed graphs have one-way edges; undirected graphs have two-way edges.

Question 4

How do you create a graph using a library like NetworkX?

Answer 4

Use functions to add nodes and edges to a graph object.

Question 5

When should you use an adjacency list instead of a matrix?

Answer 5

For sparse graphs where memory efficiency is important.

Question 6

What’s the complexity of adding/removing edges in lists vs matrices?

Answer 6

Both are O(1), but adjacency lists use less memory in sparse graphs.

Question 7

What are the pros and cons of adjacency lists and matrices?

Answer 7

Lists save space and are good for sparse graphs; matrices allow fast lookups but use more space.

Question 8

What does an adjacency list with node A pointing to B and C mean?

Answer 8

Node A is connected to nodes B and C.

Question 9

How do you represent a weighted directed graph?

Answer 9

Use nested mappings where each edge has an associated weight.