Added Day 10 & 11 codes in CPP

[YashMeh]

Please make sure you have done the following:

• [x] Created a folder with the name of language you code inside /Day<n>/ directory (Where n is for nth day)
• [x] Added your Codes
• [x] Tested your codes
• [x] Added credits (author and date) at the top of the code
• [x] Updated README.md
• [ ] Added yourself as a contributor using all-conributors-cli

[aaditkamat]

Follow the Pull Request Process and Contribution Guidelines to add yourself as a contributor. You can add changes to the respective files in this PR as well.