added cycle detection algorithms for graphs

[sabirali2560]

Fixes #

Checklist:

• 4 space indentation.
• Coding conventions are followed.
• Input is taken dynamically.
• Sample Input / Output is added at the end of file.
• Logic Documentation (Comments).
• File names are correct.

Make sure these boxes are checked before your pull request (PR) is ready to be reviewed and merged. Thanks!

Changes proposed in this pull request:

Languages Used:

Files Added:

We're happy to help you get this ready -- don't be afraid to ask for help.

Thanks!