C ++ primer-const_iterator and const-type iterator

Each container type defines its own iterator type.

Take the vector container as an example: vector <int >:: iterator ITER;

In addition, each container type also defines a const_iterator type, which can only be used to read elements in the container, but cannot be changed:

For (vector <string >:: const_iterator iter = test. Begin (); iter! = Test. End (): ++ ITER)

Cout <* ITER <end; // correct

But if you want to change its value:

* Iter = ""; // Error

Let's look at const's iterator: It must be initialized when declaring a const iterator, and then its value cannot be changed:

Vector <int> Nums (10 );

Const vector <int >:: iterator CIT = nums. Begin ();

* CIT = 1; // correct

++ Cit; // Error

This is an easy-to-Forget technical detail.