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How to use vector_ How to use vector pointer

2022-07-06 23:57:00 【Java architects must see】

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));

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

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