C + + Learning Note (ix): vector use

Standard library type,vector represents a collection of objects, where all objects are of the same type. About vectors can be understood by comparing the groups. In some ways it is like the array.

It should be noted that the vector is a class template. The template itself is not a class or function, since it is called a template, it can be understood in fact a reference standard.

When you use a template, you need to indicate what type the compiler should define the objects in the template.

This is defined in the following way:

Vector<int> num; Num is a container that holds an int type Object

Note:vectors can accommodate most types of objects as their elements, but because the reference is not an object, the vector cannot contain references.

Initialization

Vector<t> v1 v1 is an empty vectorwith an element type of T type

Vector<t> v2 (v1) assigns all elements in the V1 to v2

Vector<t> v2 = v1 equivalent to the previous sentence

Vector<t> v3 (n,val) v3 has n repeating elements, each with a value of Val

Vector<t> v4 (N) V4 has n elements, each element is the default value

Vector<t> v5{a, B,c,...} Initialization of lists

Vector<t> v5={a, B,c,...}

Note the difference between {} and ().

Use push_back to add elements like vectors :

Push_back is a member function of a vector that can add a value as the last element of a vector.

Cases:

Vector<.int> v2;

for (int i = 0; I!=100; i++)

V2.push_back (i);

Note: Because vectors can add elements efficiently and quickly at run time. Therefore , it is sometimes unnecessary to define the size of a vector . Even the definition will be superfluous.

Other vector operations:

V.empty () if v is empty, returns True

V.size () returns The number of elements in V

V[] returns a reference to the nth element in v

<,<=,>,>=,!=,== are compared in dictionary order

C + + Learning Note (ix): vector use