4D

1. struct,class Constructor

The first parameter in the copy constructor has the same type as the class, structure, or union for which it is defined. The first parameter can be a reference to the type but not the type itself.

 

2. struct 与 class区别

 （1） 默认继承权限。如果不明确指定，来自class的继承按照private继承处理，来自struct的继承按照public继承处理； 

  (2) 成员的默认访问权限。class的成员默认是private权限，struct默认是public权限。 

 

3. dynamic programming 

f(i) = max( f(j)+1 ) (j < i && envelope i is bigger than j)