My solutions to programming problems on UVA Online Judge.
If you also want to get started with programming challenges I would highly recommend that you study using Competitive Programming 3. This excellent book covers all the important algorithms that you need to know in order to be successful in your competitive programming career. Not only that, it will actually make a much better programmer and a problem solver out of you.
Should you wish to try solving problems using UVA, I recommend using JUva - a command-line tool I wrote that allows you to manage your solutions and submit them to UVA directly without using a browser.