Can any one suggest what is the best way to write good code that is understandable without a single line of comments?
I think code can be self-documenting to a large degree, and I think it's crucial, but reading even well-written code can be like looking at cells of the human body with a microscope. It sometimes takes comments to really explain the big picture of how pieces of the system fit together, especially if it solves a really complex and difficult problem.
Think about special data structures. If all that computer scientists had ever published about data structures were well-written code, few would really understand the relative benefit of one data structure over another -- because Big-O runtime of any given operation is sometimes just not obvious from reading the code. That's where the math and amortized analysis presented in articles come in.