How to use vector_ How to use vector pointer

Hello everyone , I'm wang Jun , An architect who can write code and recite poetry . Let's talk about it today vector How to use _vector How to use the pointer , I hope it can help you make progress !!!

One 、 What is? vector？

vector （Vector） Is a sequential container that encapsulates dynamic size arrays （Sequence Container）. Like any other type of container , It can hold all kinds of objects . We can simply think that , A vector is a dynamic array that can hold any type of data .

Two 、 Container characteristics

1. Sequential sequence

The elements in the order container are ordered in strict linear order . You can access the corresponding element by its position in the sequence .

2. The dynamic array

It supports fast and direct access to any element in the sequence , You can even do this through pointer arithmetic . Provides a relatively fast way to add... At the end of a sequence / Delete element operation .

3. Memory allocator aware （Allocator-aware）

The container uses a memory allocator object to dynamically handle its storage requirements .

3、 ... and 、 Basic function implementation

1. Constructors

vector(): Create an empty vector vector(int nSize): Create a vector, The number of elements is nSize vector(int nSize,const t& t): Create a vector, The number of elements is nSize, And the values are t vector(const vector&): copy constructor vector(begin,end): Copy [begin,end) The element of another array in the interval to vector in

2. Add function

void push_back(const T& x): Add an element to the tail of the vector X emplace_back: Add an element to the tail of the vector X The following two are equal

std::vector<Vertex> MM;
MM.push_back(Vertex(a));

Copy

I only heard the voice of the architect from the architect's office : The mountains and rocks are really small , Bats fly in the temple at dusk . Who's going to answer the first couplet or the second couplet ?

 This code is created by Java Architects must see the net - Structure Sorting 
std::vector<Vertex> MM;
MM.emplace_back(a);

Copy

iterator insert(iterator it,const T& x): An element is added before the iterator points to the element in the vector x iterator insert(iterator it,int n,const T& x): The iterator in the vector is added before the element n The same elements x iterator insert(iterator it,const_iterator first,const_iterator last): Vector in which the iterator inserts another vector of the same type before pointing to the element [first,last) Data between

3. Delete function

iterator erase(iterator it): Delete the iterator pointing element in the vector iterator erase(iterator first,iterator last): Delete the vector [first,last) Medium element void pop_back(): Delete the last element in the vector void clear(): Empty all the elements in the vector

4. Traversal function

reference at(int pos): return pos References to location elements reference front(): Returns the reference to the first element reference back(): Returns the reference to the tail element iterator begin(): Returns the vector header pointer , Point to first element iterator end(): Return vector tail pointer , Point to the next position of the last element of the vector reverse_iterator rbegin(): reverse iterator , Point to last element reverse_iterator rend(): reverse iterator , Point to the position before the first element

5. Judgment function

bool empty() const: Judge whether the vector is empty , If it is empty , Then there are no elements in the vector

6. The size function

int size() const: Returns the number of elements in a vector int capacity() const: Returns the maximum element value that the current vector can hold int max_size() const: Return the maximum allowed vector The number of elements

7. Other functions

void swap(vector&): Exchange data between two vectors of the same type void assign(int n,const T& x): Set the front of the vector n The value of each element is x void assign(const_iterator first,const_iterator last): Vector [first,last) Set the element in the current vector element

8. Look at it clearly

1.push_back Add a data at the end of the array

2.pop_back Remove the last data of the array

3.at Get the data of the number position

4.begin Get a pointer to the array header

5.end Get the last cell of the array +1 The pointer to

6．front Get a reference to the array header

7.back Get a reference to the last cell of the array

8.max_size obtain vector The biggest is how big

9.capacity At present vector The size of the allocation

10.size The size of the data currently used

11.resize Change the size of the currently used data , If it's bigger than what's currently in use , Fill in the default value

12.reserve To change the current vecotr The size of the space allocated

13.erase Delete the data item that the pointer points to

14.clear Clear the current vector

15.rbegin take vector The reverse start pointer returns ( In fact, it is the original end-1)

16.rend take vector The end pointer of the reverse construct returns ( In fact, it is the original begin-1)

17.empty Judge vector Is it empty

18.swap And another vector Exchange data

That's the end of today's article , Thank you for reading ,Java Architects must see I wish you a promotion and a raise , Good luck every year .