Container vector and iterator + usage

Container vector declaration method: vector <type>: variable name (parameter)

Reference # incude <vector> before use

There are several initialization methods:

1 declaration initialization example: vector <int> VCT; default constructor is empty

Vector <int> vct1 (VCT) is initialized using declared containers.

The containers whose vector <int> vct2 (3, 5) is 3 are initialized and all three are equal to 5.

Vector <int> vct3 (5) is 3 and the initial value is 0.

2 vector is an ordered container and can be read through the subscript operator, but it must be an element that already exists in the container. Otherwise, an error will occur.

To facilitate traversal, each container has its own iterator.

Iterator concept: Used to traverse elements in a container and access the value of elements.

Declare the iterator vector of an integer container <int>: itrator itr;

Traverse elements in a container

For (itr = VCT. Begin (); I! = VCT. end (); itr ++)/* pay attention to VCT. end () is the next element of the last element in the container. It is a non-existent element. If the vector is empty, end is the same as the iterator returned by begin.

Cout <* itr; // here, * is the unreferenced operator. End cannot use * or the auto increment or decrement operator.

Another type of iterator is const_itrator. It can only access elements in the container, but cannot change elements.

Note: const vector <int >:: itrator is not equal to vector <int >:: const_itrator

The former can only access fixed elements and cannot perform operations such as * itr ++.