feat: LFU (Least frequently used) cache

[corvo-007]

Description of Change

LFU Cache implementation
In a fixed size cache, when new item is added and the cache is full
The least frequently used element is evicted from the cache

If there are multiple items with the same frequency of usage,
then the least recently used item is evicted.

Checklist

• Added description of change
• Added file name matches File name guidelines
• Added tests and example, test must pass
• Added documentation so that the program is self-explanatory and educational - Doxygen guidelines
• Relevant documentation/comments is changed or added
• PR title follows semantic commit guidelines
• I acknowledge that all my contributions will be made under the project's license.

Notes:

added LFU Cache with tests and usage.

[realstealthninja]

Thank you for your contribution! Let me know if this was for hacktoberfest

[corvo-007]

Thank you for your contribution! Let me know if this was for hacktoberfest

Yes, this is for Hacktoberfest. Thank you for reviewing my contribution.

[realstealthninja]

Thank you for your contribution! Let me know if this was for hacktoberfest

Yes, this is for Hacktoberfest. Thank you for reviewing my contribution.

youre very welcome. lets get this accepted soon 🚀

[corvo-007]

@realstealthninja, what is the reason for making a non member function static?
And should I make test1() and test2() static as well?

[realstealthninja]

@realstealthninja, what is the reason for making a non member function static?
And should I make test1() and test2() static as well?

Static is used to hide the function from the global namespace.

Imo there shouldn't be 3 test function just one with comments delimiting the cases

[corvo-007]

@realstealthninja, what is the reason for making a non member function static?
And should I make test1() and test2() static as well?

Static is used to hide the function from the global namespace.

Imo there shouldn't be 3 test function just one with comments delimiting the cases

Got it.

[realstealthninja]

Lgtm