Read Me

Full Disclosure

I read the project documentation last night, understood the problem with @contents.dup then slept on it and started actual work this evening. I started by forking the GitHub repo and was already working on a fix when I realized I was working on code that did not have the naive dup statement.

So I can't take credit for the change tracking approach even though I swear that was on my mind. I can however take credit for a further > 50% reduction in memory footprint.

localhost:rmu-entrance-exam ehles$ rake test:ali_rizvi
Starting Memory:
1896
Adding 100 characters, 1 at a time
Current memory footprint:
1976
Adding 1000 characters, 1 at a time
Current memory footprint:
2620
Adding 10000 characters, 1 at a time
Current memory footprint:
11196
Adding 100000 characters, 1 at a time
Current memory footprint:
89344
Took 0.423752s to run
Loaded suite /Users/ehles/.rvm/gems/ruby-1.8.7-p352/bin/rake
Started
..........
Finished in 0.001039 seconds.

10 tests, 14 assertions, 0 failures, 0 errors
localhost:rmu-entrance-exam ehles$ rake test:ali_rizvi_fixed
Starting Memory:
1900
Adding 100 characters, 1 at a time
Current memory footprint:
1992
Adding 1000 characters, 1 at a time
Current memory footprint:
2768
Adding 10000 characters, 1 at a time
Current memory footprint:
11492
Adding 100000 characters, 1 at a time
Current memory footprint:
89596
Took 0.53237s to run
Loaded suite /Users/ehles/.rvm/gems/ruby-1.8.7-p352/bin/rake
Started
..........
Finished in 0.001057 seconds.

10 tests, 14 assertions, 0 failures, 0 errors
localhost:rmu-entrance-exam ehles$ rake test:mine
Starting Memory:
1904
Adding 100 characters, 1 at a time
Current memory footprint:
1956
Adding 1000 characters, 1 at a time
Current memory footprint:
2288
Adding 10000 characters, 1 at a time
Current memory footprint:
6016
Adding 100000 characters, 1 at a time
Current memory footprint:
34064
Took 0.354141s to run
Loaded suite /Users/ehles/.rvm/gems/ruby-1.8.7-p352/bin/rake
Started
..........
Finished in 0.001017 seconds.

10 tests, 14 assertions, 0 failures, 0 errors
localhost:rmu-entrance-exam ehles$ 

Next Steps

These are some things I would consider for an actual project

• Enforce a maximum limit on the @commands an @reverted arrays
• Serialize the commands to a TempFile on disk
• Memoize the contents method (being sure to erase the memoized copy when actions are preformed)