Add new resource for Graph Theory course

[Muditapandey26]

What does this PR do?

Add resource

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For resources

Description

"An Introduction to Graph Theory" is a full-length lecture series by Dr. Sarada Herke, covering core graph theory concepts such as paths, cycles, connectivity, trees, bipartite graphs, Euler & Hamilton graphs, and graph coloring. The series is structured clearly and explains both theory and intuition using examples, making it beginner-friendly.

Why is this valuable (or not)?

This resource is valuable because it provides a strong conceptual foundation in graph theory using simple explanations rather than heavy formalism. Graph Theory is widely used in computer science (data structures, networks, algorithms), competitive programming, and discrete mathematics, so this course supports students in multiple learning areas.

How do we know it's really free?

This course is hosted on YouTube and publicly available to watch without login, payment, or sign-up. No email or enrollment is required.

For book lists, is it a book? For course lists, is it a course? etc.

It is a course (video lecture playlist) and should be added under the Graph Theory section of Courses.

Checklist:

• Search for duplicates.
• Include author(s) and platform where appropriate.
• Put lists in alphabetical order, correct spacing.
• Add needed indications (PDF, access notes, under construction).
• Used an informative name for this pull request.

Follow-up

• Check the status of GitHub Actions and resolve any reported warnings!

[github-actions]

Linter failed, fix the error(s):

free-programming-books/courses/free-courses-en.md
879:1-884:115  warning  Alphabetical ordering: swap l.880 and l.879  alphabetize-lists  remark-lint

[github-actions]

Linter failed, fix the error(s):

free-programming-books/courses/free-courses-en.md
879:1-884:115  warning  Alphabetical ordering: swap l.883 and l.882  alphabetize-lists  remark-lint