Implement Trapped Rain Water using Dynamic Programming Strategy.

[TruongNhanNguyen]

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
• Search previous suggestions before making a new one, as yours may be a duplicate.
• I acknowledge that all my contributions will be made under the project's license.

[TruongNhanNguyen]

Let's take a look on this PR @realstealthninja & @Panquesito7

[mrmagic2020]

The code looks pretty solid and is well-documented. Not sure if modification of DIRECTORY.md is needed. What do you think @realstealthninja?

[mrmagic2020]

👍

[github-actions]

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[github-actions]

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