C++ Tutorials

C++ Tutorials

Syntax:
vector_name.insert (position, val)
Syntax:
vector_name.insert(position, size, val)
Syntax:
vector_name.insert(position, iterator1, iterator2)
Use std::deque for this, that's what it was designed for.

We will learn about Vectors. Vectors are same as dynamic arrays with the ability to resize itself automatically when an element is inserted or deleted, with their storage being handled automatically by the container.

Vector elements are placed in contiguous storage so that they can be accessed and traversed using iterators. In vectors, data is inserted at the end. Inserting at the end takes differential time, as sometimes there may be a need of extending the array.

Removing the last element takes only constant time, because no resizing happens. Inserting and erasing at the beginning or in the middle is linear in time. We can declare a vector using this statement;. We need to import the vector library to use vector in our program.

Here, I am declaring an integer vector v. To insert values into a vector, we have to use the push_back function. Here, I am iterating from 1 to 5 and pushing ith value in the vector. We can access the values just like we do in arrays.

Let’s run this code, we can see that all the values in the vector are printed. To print the size of a vector, we can use the size function. We can use the capacity function to returns the size of the storage space currently allocated to the vector expressed as number of elements To check whether a vector is empty or filled, we use the empty function.

It returns 1 is the vector is empty. To print the maximum size of array, we use the max_size function. Let’s run this code, we can see that the size of vector is 5, its capacity is 8 and clearly the vector is not empty, this is the maximum size this vector can store.

To print the first and last element of the array, we use the front and back operators. To print the ith element of the array, we use the at function. Let’s run this code, we can see that the output is as expected. So, this brings us to the end of this video tutorial.

C++ vector append

Best way to append vector to vector

c++ vector::insert at index vector<>::insert is designed to add elements so it’s the most adequate solution.

You could call reserve on the destination, vector to reserve some space, but unless you add a lot of vector together, it’s likely that it won’t provide many benefits: vector<>::insert know how many elements will be added, you will avoid only one reserve call.

Erase vector c++

std::remove() instead:

#include <algorithm>
...
vec.erase(std::remove(vec.begin(), vec.end(), 8), vec.end());
std::vector<int> vec;

vec.push_back(6);
vec.push_back(-17);
vec.push_back(12);

// Deletes the second element (vec[1])
vec.erase(vec.begin() + 1);
Or, to delete more than one element at once:

// Deletes the second through third elements (vec[1], vec[2])
vec.erase(vec.begin() + 1, vec.begin() + 3);

C++ vector::insert at end

Push_back() function is used to push elements into a vector from the back. The new value is inserted into the vector at the end, after the current last element and the container size is increased by 1. 1. Strong exception guarantee – if an exception is thrown, there are no changes in the container.

Yes, it is well defined. Assume if vector is empty, begin() equals to end(). The effects is it inserts a copy of element before iterator.

§ Table 100 — Sequence container requirements (in addition to container)

|------------------------------------------------------------------|
|a.insert(p,t)  | iterator    Requires:T shall be CopyInsertable into   X. For          |
|               |             vector and deque, T shall also be CopyAssignable. |
|               |             Effects: Inserts a copy of t before p.           

Vector push_back c++

std::vector manages its own memory. That means that, when the destructor of a vector is invoked the memory held by the vector is released. std::vector also invokes an object’s destructor when it is removed (through erasepop_backclear or the vector’s destructor).

When you do this:

Radio newradio(radioNum);
m_radios.push_back(newradio);

Method 1

std::vector<int> vec = { 1 };
vec.push_back(2);
vec.push_back(3);
vec.push_back(4);
vec.push_back(5);

Method 2

std::vector<int> vec = { 1 };
int arr[] = { 2,3,4,5 };
vec.insert(std::end(vec), std::begin(arr), std::end(arr));