C++Usage of vector Container in C++

In c++In which, vector is a very useful container, the following is a summary of this container.

1 Basic operations

(1)Header file #include<vector>.

(2)Create vector object, vector<int> vec;

(3)Insert number at the end: vec.push_back(a);

(4)Use index to access elements, cout<<vec[0]<<endl;Remember that the index starts from 0.

(5)Use iterator to access elements.

vector<int>::iterator it;
for(it=vec.begin();it!=vec.end();it++)
cout<<*it<<endl;

(6)Insert element: vec.insert(vec.begin()+i,a);At the i+1elements before inserting a;

(7)Delete element: vec.erase(vec.begin()+2);Delete the3elements

vec.erase(vec.begin()+i,vec.end()+j);Delete interval [i,j-1);Interval starts from 0

(8)Vector size: vec.size();

(9)Clear: vec.clear();

2

The elements of vector can not only be int, double, string, but also structures. However, attention must be paid: the structure must be defined globally, otherwise an error will occur. The following is a short program code:

#include<stdio.h>
#include<algorithm>
#include<vector>
#include<iostream>
using namespace std;
typedef struct rect
{
int id;
int length;
int width;
　　//For vector elements that are structures, comparison functions can be defined within the structure. The following is sorted in ascending order by id, length, and width.
　　bool operator< (const rect &a) const
{
if(id!=a.id)
return id<a.id;
else
{
if(length!=a.length)
return length<a.length;
else
return width<a.width;
}
}
}Rect;
int main()
{
vector<Rect> vec;
Rect rect;
rect.id =1;
rect.length =2;
rect.width =3;
vec.push_back(rect);
vector<Rect>::iterator it = vec.begin();
cout << (*it).id << ' ' << (*it).length << ' ' << (*it).width << endl; 
return 0;
}

3 Algorithm

(1) Use reverse to reverse the elements: need header file #include <algorithm>;

reverse(vec.begin(), vec.end()); Reverse the elements (in the vector, if a function needs two iterators,

Generally, the latter does not include.)

(2Use sort to sort: need header file #include <algorithm>;

sort(vec.begin(), vec.end()); (The default is to sort in ascending order, that is, from small to large).

You can rewrite the sorting comparison function to compare in descending order as follows:

Define the sorting comparison function:

bool Comp(const int &a, const int &b)
{
return a > b;
}

When calling: sort(vec.begin(), vec.end(), Comp), this will sort in descending order.

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