Added Space Optimized Solution to Subset sum problem

[Rupa-Rd]

Solved #5600

• [x] I have read CONTRIBUTING.md.
• [x] This pull request is all my own work -- I have not plagiarized it.
• [x] All filenames are in PascalCase.
• [x] All functions and variable names follow Java naming conventions.
• [x] All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• [x] All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 62.77%. Comparing base (79544c8) to head (b9a12fe).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5612      +/-   ##
============================================
- Coverage     62.77%   62.77%   -0.01%     
- Complexity     4020     4024       +4     
============================================
  Files           564      565       +1     
  Lines         15932    15939       +7     
  Branches       3073     3076       +3     
============================================
+ Hits          10001    10005       +4     
- Misses         5520     5521       +1     
- Partials        411      413       +2     

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[Rupa-Rd]

There are no files changed in this PR

@siriak, Kindly verify it!

[Rupa-Rd]

Please add JUnit tests

@siriak Added JUnit test.