Vector declaration type in c++

Question

请任何人向我解释这意味着什么？

vector<int> myvector(4,99);  

Answer 1

它（最有可能是）一个std :: vector整数，被初始化为包含四个值为99的整数。

Answer 2

A a(x,y); creates an object called a , calling a constructor of A with two parameters matching the types of x and y , or any convertible types.

So this:

vector<int> myvector(4,99);

Matches this constructor:

explicit vector( size_type num, const TYPE& val = TYPE() ); 
// `TYPE` is a `typedef` assigned to the parametrized type (here `int`), which means the constrcutor is actually:
explicit vector( size_type num, const int& val = int() );

Which constructs a vector with 4 elements of value 99 and calls it myvector . This constructor is called because the first parameter can be converted to a size_type , which is also a typedef , defined to an integral type (usually unsigned long ).