template<
class T,
class Allocator = std::allocator<T>
> class vector;
To use Vector on your code, you must include #include <vector>.
#include <vector>
#include <iostream>
int main(void)
{
std::vector<int> v;
v.push_back(1);
v.push_back(2);
v.push_back(3);
for (int i = 0; i < v.size(); i++)
{
std::cout << v[i] << std::endl;
}
return 0;
}
output
1
2
3
<aside>
⚠️ to compilers
g++ -std=98 main.cpp
</aside>
There is a critical point when initializing the value on the declaration line will get an error when trying compiler with c++98.
#include <vector>
#include <iostream>
int main(void)
{
std::vector<int> v = {1, 2, 3, 4, 5};
for (int i = 0; i < v.size(); i++)
{
std::cout << v[i] << std::endl;
}
return 0;
}
To compile I use g++ -std=98 main.cpp
main.cpp:6:22: error: in C++98 ‘v’ must be initialized by constructor, not by ‘{...}’
6 | std::vector<int> v = {1, 2, 3, 4, 5};
| ^
main.cpp:6:40: error: could not convert ‘{1, 2, 3, 4, 5}’ from ‘<brace-enclosed initializer list>’ to ‘std::vector<int>’
6 | std::vector<int> v = {1, 2, 3, 4, 5};
| ^
| |
| <brace-enclosed initializer list>
<aside>
⚠️ If compiled with -std=c++11 ****will work with you without error. The reason for that's c++98 doesn’t support the initial list with vector.
</aside>
Returns a reference to the element at position n in the vector container.
<aside> 🚫 Don’t initiate value by using a list, it will not compile with c++98.
</aside>
The size of the currently allocated storage capacity in the vector is measured in terms of the number of elements it can hold.
#include <iostream>
#include <vector>
int main ()
{
std::vector<int> myvector;
// set some content in the vector:
for (int i=0; i<100; i++) myvector.push_back(i);
std::cout << "size: " << (int) myvector.size() << '\\n';
std::cout << "capacity: " << (int) myvector.capacity() << '\\n';
std::cout << "max_size: " << (int) myvector.max_size() << '\\n';
return 0;
}
size: 100
capacity: 128
max_size: 1073741823
