Use this repo for contributing in open source. Start solving issues and raise the pull requests and even you can create your own issues. If you want to contribute to a project, the simplest way is to:
Find a ISSUE you want to contribute to ->> Fork it
Clone it to your local system
Make a new branch
Make your changes
Push it back to your repo
Click the Compare & pull request button
Click Create pull request to open a new pull request
If the reviewers ask for changes, repeat steps 5 and 6 to add more commits to your pull request.
The implementations/codes which are added/merged in CPP-:
Happy coding!