Solve BVP numerically

You can also find the above content in the following link (I got permitted by the author of the article in the link, because it is me):

https://zhuanlan.zhihu.com/p/638256833

For more details of the algorithm used above, see this book, Numerical Recipes in C book set Numerical Recipes in C The Art of Scientific Computing, Second Edition (William H. Press, Brian P. Flannery etc.). 

I post it on Bilibili just to take some notes, and I am not willing to answer the question from strangers. If you are acquainted with me, please discuss with me via e-mail or some other communication softwares.