Catalog

One 、vector Statement of （ initialization ）

Two 、 increase ： Additive elements

3、 ... and 、 Delete ： Remove elements

Four 、 Change ： Modifying elements

5、 ... and 、 check ： Traversing elements

summary

Preface

C++ STL Is a very powerful container Library , Where dynamic array vector It is one of the most convenient containers . Next up vector Some basic operations , The main operation is still “ increase Delete Change check ”：

One 、vector Statement of （ initialization ）

vector  It's a vector type , It can hold many types of data , Such as several integers , This article takes storage shaping as an example .

Yes vector There are several common ways to initialize , Just master the red marking ：

（1）vector <int> ver = vector<int>(); or  vector <int> ver;// Defined at this time ver The space occupied is uncertain , New spaces can be added dynamically

（2） vector<int> ver(10); // Defined 10 The vector of an integral element （ The angle bracket is the element type name , It can be any legal data type ）, But no initial value is given , Its value is uncertain .

（3）vector<int> ver(10,1); // Defined 10 The vector of an integral element , And the initial value of each element is 1

（4）vector<int> ver(b); // use b Vector to create ver vector , Overall replicability assignment

（5）vector<int> ver(b.begin(),b.begin+3); // Defined ver The value is b pass the civil examinations 0 One to the first 2 individual （ common 3 individual ） Elements

（6）int b[7]={1,2,3,4,5,9,8}; vector<int> ver(b,b+7); // Get the initial value from the array

（7）vector<vector<int>> ver; // Two dimensional vector

Two 、 increase ： Additive elements

int t;

cin>>t;

ver.push_back(t);// take t Add to vector End of array
ver.push_front(t);// take t Add to vector At the beginning of the array
ver.insert(ver.begin()+n, t);// take t Insert into ver.begin()+n  Parameters here cannot be written int type , Pointer should be written ！！
Be careful ：

If use cin>> Enter data or use subscript ver[i]=t assignment , that vector There must be space , It can be used resize() Give space or use directly push_back(t) Just add elements .

It can also be used during initialization vector <int> ver(n); In this way, we can cin>> Enter data or use subscript ver[i]=t assignment , But this can't be used push_back(t) Add data , because push_back(t) Is to add data to the end ！！！ The former n The default is 0,push_back(t) It will not be modified before n The value of .

3、 ... and 、 Delete ： Remove elements

ver.erase(iterator p);// Delete iterator p The element pointing to the position

ver.erase(ver.begin()+1,ver.begin()+3); // Delete a pass the civil examinations 1 individual （ From 0 Count on it ） To the first 2 Elements , That is to say, deleted elements from a.begin()+1 Count up （ Including it ） Until a.begin()+ 3（ It's not included ）

ver.pop_back();// Delete the last element
ver.pop_front();// Delete first element

Four 、 Change ： Modifying elements

To be added ing…… See the summary for details

5、 ... and 、 check ： Traversing elements

// There are two ways to traverse elements ：

//1. Subscript traversal  
for (int i = 0; i < n; i++)
    cout << ver[i] << " ";

//2. Iterator traversal vector <int>::iterator p;
for(auto p=ver.begin();p!=ver.end();p++)
    cout << *p << " ";
among auto representative vector <int>::iterator（ Iterator type ）
Be careful ：*(p+1)== *(ver.begin()+1) == ver[i+1]

summary

vector It also contains functions with various functions , Summarized below （ part ）：

push_back()  // Add a data at the end of the array

pop_back() // Remove the last data of the array

at()  // Get the data of the number position

begin() // Get a pointer to the array header

end() // Get the last cell of the array +1 The pointer to

find()  // Determine whether an element exists

front() // Get a reference to the array header

back() // Get a reference to the last cell of the array

max_size() // obtain vector The biggest is how big

capacity() // At present vector The size of the allocation

size() // The size of the data currently used

capacity(); // return a The total number of elements that can be held in memory

a.reserve(100); // To change the current vecotr The size of the allocated space will a The capacity of （capacity） Expand to 100, That is to say, test now a.capacity(); The return value is 100

a.resize(10); // take a Set the number of existing elements to 10 individual , Delete more , Less is more , The default value of the added element is 0

a.resize(10,2); // take a Set the number of existing elements to 10 individual , Delete more , Less is more , The value of the added element is 2

erase() // Delete the data item that the pointer points to

clear() // Clear the current vector

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

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

empty() // Judge vector Is it empty

swap() // And another vector Exchange data

a.swap(b); //b Vector , take a The elements in and b The elements in are exchanged as a whole

reverse(obj.begin(),obj.end()); reverse iterator , Realize element exchange

find(nums.begin(), nums.end(), target)// The return is target The first address , If the return tail address is not found nums.end()

sort(a.begin(),a.end(),cmp); // Yes a From a.begin()（ Including it ） To a.end()（ It's not included ） The elements are arranged from small to large cmp Customizable , There can be no （ If not, the default is from small to large ）

copy(a.begin(),a.end(),b.begin()+1); // hold a From a.begin()（ Including it ） To a.end()（ It's not included ） Copy the elements of to b in , from b.begin()+1 The location of ( Including it ) Start copying , Cover the original elements .