Level of Qustion:
Finish:
* easily
** trouble(麻烦)
***hard(Need check book or other information)
Not:
+ easy understand&after look can code by myself
++ hard understand&after look can code by myself
+++ hard understand&hard to recode by myself
Level of Qustion:Record the difficult level of Problem For future review
原文：https://www.cnblogs.com/Marigolci/p/11308216.html