message: Updated USEFUL_RESOURCES.md
  Added Competitive Programmer's handbook
diff: [Narasimha Karumanchi - Data structures and algorithms made easy](https://github.com/MethkupalliVasanth/Books/blob/master/Narasimha%20Karumanchi%20-%20Data%20structures%20and%20algorithms%20made%20easy%20(0%2C%20CareerMonk).pdf) An important book to learn must needed algorithms for interviews
  +[Competitive Programmer's Handbook](https://cses.fi/book/book.pdf)
  +
  