Request to add Trapping Rain Water in misc.

[AnuragKumar007]

It's my 1st PR. I want to add Classic question "Trapping Rainwater" in misc folder. I've tried my best to keep the code neat & clean. Also used comments to make the code easy to understand for all.
Request to add a Classic Question.

Describe your change:

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Documentation change?

References

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Java files are placed inside an existing directory.
• All filenames are in all uppercase characters with no spaces or dashes.
• All functions and variable names follow Java naming conventions.
• All new algorithms have a URL in its comments that points to Wikipedia or other similar explanation.
• If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.

[gkgaurav31]

In line 39,

trappedWater += waterLevel - height[i]; //width =1

It will have negative value (which is not possible for water trapped) if height[i] is more than both leftMax[i] and rightMax[i].

We can fix that in the following way:

//If the currentHeight is more than the max on left and right both, take 0.
trappedWater += Math.max(0, Math.min(leftMax[i],rightMax[i])-height[i]);

[AnuragKumar007]

Thanks! but can you tell me the test case too?
I think the code is correct. Let's take an array - {3,0,5,2,0,2}
it should give output - 5 and it's giving

[gkgaurav31]

Just noticed, the way you've generated the prefix/suffix array takes care of this edge case. Should be okay.

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[siriak]

The code looks good, could you please add some JUnit tests? (see https://github.com/TheAlgorithms/Java/tree/master/src/test/java/com/thealgorithms)

[github-actions]

Please reopen this pull request once you commit the changes requested or make improvements on the code. If this is not the case and you need some help, feel free to seek help from our Gitter or ping one of the reviewers. Thank you for your contributions!