Part.I Attention

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vectorPoints to note when using :

add citation#include <vector>
It can be called directly as an "array", but! If you want to modify the value in the function, you must add it &! ! !

Some tricks:

// 将 b 中的元素去重并从小到大排序
sort(b.begin(),b.end());
b.erase(unique(b.begin(),b.end()),b.end());

Part.II Function

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Function list:

Function name	meaning
`begin()`	Returns an iterator pointing to the first element in the container.
`end()`	Returns an iterator pointing to the position after the last element of the container, usually `begin()`used in conjunction with .
`rbegin()`	Returns an iterator pointing to the last element.
`rend()`	Returns an iterator pointing to the position preceding the position of the first element.
`size()`	Returns the actual number of elements.
`max_size()`	Returns the maximum number of elements. This is usually a large value, usually 232-1, so we rarely use this function.
`resize()`	Change the number of actual elements.
`capacity()`	Returns the current capacity.
`empty()`	Determine whether there is an element in the container, if there is no element, return true; otherwise, return false.
`reserve()`	Increase the capacity of the container.
`shrink _to_fit()`	Reduce memory to equal the size actually used by the current element.
operator`[]`	The [ ] operator is overloaded, and the elements in the vector container can be accessed or even modified through subscripts like accessing elements in an array.
`at()`	Elements are accessed using a bounds-checked index.
`front()`	Returns a reference to the first element.
`back()`	Returns a reference to the last element.
`data()`	Returns a pointer to the first element in the container.
`assign()`	Replace existing content with new elements.
`push_back()`	Adds an element to the end of the sequence.
`pop_back()`	Removes the element from the end of the sequence.
`insert()`	Inserts one or more elements at the specified positions.
`erase()`	Moves out an element or a block of elements.
`clear()`	All elements are removed and the container size becomes 0.
`swap()`	Swaps all elements of two containers.
`emplace()`	Generates an element directly at the specified position.
`emplace_back()`	Generates an element at the end of the sequence.

Chap.I Constructor

vector(): Create an empty vector
:vector(int nSize) Create a vector with nSize elements
vector(int nSize,const t& t): Create a vector, the number of elements is nSize, and the value is t
:vector(const vector&) copy constructor
vector(begin,end): Copy [begin,end)the elements of another array in the range to the vector

Here is an example of calling the constructor:

// 定义了10个整型元素的向量，初始化为 1
vector<int> a(10,1); 	
// 定义一个二维 vector 向量，所有元素初始化为 1
vector<int> a(10,1);
vector<vector<int>> aa(10,a);
// 通过 int[] 构造并初始化 vector
int b[7] = {
    
    1,2,3,4,5,9,8}; 
vector<int> a(b,b+7);
// 直接用数组构造
vector<int> a({
    
    1,2,3,4,5,9,8});

Chap.II Add function

void push_back(const T& x): add an element X at the end of the vector
iterator insert(iterator it,const T& x): Add an element x before the iterator in the vector points to the element
iterator insert(iterator it,int n,const T& x): Add n identical elements x before the iterator in the vector points to the element
iterator insert(iterator it,const_iterator first,const_iterator last)[first,last): Insert the data between another vector of the same type before the iterator in the vector points to the element

The following is a simple operation example:

vector<int> a(10,1);	// 10个1
auto itr=a.begin()+3;	// 得到第 3 个迭代器
a.insert(itr,2,8);		// 在迭代器的位置处插入 2 个 8，a=[1  1  1  8  8  1  1  1  1  1  1  1]

Chap.III delete function

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

The following is a simple operation example:

auto tmp=a.erase(a.begin()+2,a.begin()+4);
a.pop_back();		// 删除最后一个元素

vectorThe meaning of the first sentence: Two elements from the 3rd element to the 5th element (not included) are deleted , and the iterator of the 3rd element after deletion is returned.

Chap.IV traversal function

T at(int pos): Returns a reference to the element at position pos
T front(): Returns a reference to the first element
T back(): Returns a reference to the tail element
iterator begin(): Returns the vector head pointer, pointing to the first element
iterator end(): Returns the vector tail pointer, pointing to the next position of the last element of the vector
reverse_iterator rbegin(): reverse iterator, pointing to the last element
reverse_iterator rend():Reverse iterator, pointing to the position before the first element

Notice:

vector can []be used to get the element value of a certain index, but it cannot pythonbe sliced like that.
end()Returns the iterator after the last element, *(vec.end()-1)which is the value of the last element

vector<int> b({
    
    1,2,3,4,5,6,7,8});
cout<<b.front()<<"  "<<b.back()<<endl;		// 1  8
cout<<*b.begin()<<"  "<<*(b.end()-1)<<endl;	// 1  8

Chap.V judgment/size/other functions

bool empty() const: Determine whether the vector is empty, if it is empty, there is no element in the vector
int size() const: Returns the number of elements in the vector
int capacity() const: Returns the maximum element value that the current vector can hold
int max_size() const: Returns the maximum allowable number of vector elements
void swap(vector&): Exchange the data of two vectors of the same type
void assign(int n,const T& x): Set the value of the first n elements in the vector to x
void assign(const_iterator first,const_iterator last): [first,last)The element in the vector is set to the current vector element

	cout<<b.empty()<<endl;
    cout<<b.size()<<"  "<<b.capacity()<<"  "<<b.max_size()<<endl;
    printVec(b);
    b.assign(6,10);     // 指定 b 中的元素为6个10
    printVec(b);
    b.assign(b.begin()+1,b.end()-1); // 去掉 b 第一个元素和最后一个元素
    printVec(b);

Part.III Code

The following is Vectorthe code used in the learning process (in fact, it is a summary of the above code):

#include <iostream>
#include <iomanip>
#include <vector>

using namespace std;

int main()
{
    
    
    auto printVec=[](vector<int> vec) {
    
    for(auto& c:vec) cout << c << "  ";cout << endl;};
    // 构造
    vector<int> a(10,1);
    printVec(a);
    // 插入
    auto itr=a.begin()+3;
    auto tmp = a.insert(itr,2,8);
    cout << *(tmp+1)<<endl;
    printVec(a);
    // 删除
    tmp=a.erase(a.begin()+2,a.begin()+4);// 删除的元素不包含 itr+1
    cout <<* tmp<<endl;
    printVec(a);
    a.pop_back();
    printVec(a);
    // 修改
    a[3]=3;
    a.push_back(4);
    printVec(a);
    // 遍历
    vector<int> b({
    
    1,2,3,4,5,6,7,8});
    cout<<b.front()<<"  "<<b.back()<<endl;
    cout<<*b.begin()<<"  "<<*(b.end()-1)<<endl;
    // 其他函数
    cout<<b.empty()<<endl;
    cout<<b.size()<<"  "<<b.capacity()<<"  "<<b.max_size()<<endl;
    printVec(b);
    b.assign(6,10);     // 指定 b 中的元素为6个10
    printVec(b);
    b.assign(b.begin()+1,b.end()-1); // 去掉 b 第一个元素和最后一个元素
    printVec(b);
    getchar();
    return 0;
}

The output is as follows:

1  1  1  1  1  1  1  1  1  1
8
1  1  1  8  8  1  1  1  1  1  1  1
8
1  1  8  1  1  1  1  1  1  1
1  1  8  1  1  1  1  1  1
1  1  8  3  1  1  1  1  1  4
1  8
1  8
0
8  8  2305843009213693951
1  2  3  4  5  6  7  8
10  10  10  10  10  10
10  10  10  10

Detailed Explanation of C++ STL's Variable Length Array Vector

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