[BUG] MorrisInorder file doesn't pass the cpplint tests

[offamitkumar]

cpplint check on 'MorrisInorder.cpp' reports 107 errors.

[cclauss]

Tons of our files fail cpplint --recursive . as can be seen from studying our GitHub Action output. We force modified files to pass the test but that does not fix files that were already in the repo.

The approach of gradual compliance is often used when adding new tests to an existing codebase and we use it here. If you study our two cpplint GitHub Actions, this will become clear. If you want to attack noncompliant files with clang-format that would be supercool.