1.Medium：https://medium.com/@ivanlee_10237/planning-by-dynamic-programming-principle-coding-2ea8cc1a87e0
2.original code：https://github.com/applenob/rl_learn/blob/master/1_gridworld.ipynb
3.video(English):https://www.youtube.com/watch?v=Nd1-UUMVfz4&list=PLzuuYNsE1EZAXYR4FJ75jcJseBmo4KQ9-&index=3
4.video(Chinese):https://v.youku.com/v_show/id_XMjcwMDY1MDI1Mg==.html?spm=a2h1n.8251843.playList.5!2~5~A&f=49376145&o=1
5.refer literature:https://zhuanlan.zhihu.com/p/30518290