C + + vector usage

In C + +, vector is a very useful container, and here is a summary of the container.

1 Basic operations

(1) header file #include<vector>.

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

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

(4) Use subscript to access the element,cout<<vec[0]<<endl; remember that the subscript is starting from 0.

(5) Use iterators 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); Insert a in front of the first I+1 element;

(7) Delete element: Vec.erase (Vec.begin () +2); Delete 3rd element

Vec.erase (Vec.begin () +i,vec.end () +j); Delete interval [i,j-1]; interval starting from 0

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

(9) Empty: Vec.clear ();

2

Vector elements can not only make int,double,string, but also the structure, but note that the structure should be defined as global, otherwise it will be wrong. Here 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 structural, you can define a comparison function within the structure, sorted in ascending order of Id,length,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) Flip the element with reverse: Requires a header file #include<algorithm>

Reverse (Vec.begin (), Vec.end ()); Flips the element (in a vector, if two iterators are required in a function,

Usually the latter is not included.)

(2) Sorting by using sort: Requires header file #include<algorithm>

Sort (Vec.begin (), Vec.end ());(by default in ascending order, that is, from small to large).

You can compare functions in descending order by overriding the sort comparison, as follows:

To define a sort comparison function:

BOOL Comp (const int &A,CONST int &b)
{
Return a>b;
}
Called When: Sort (Vec.begin (), Vec.end (), Comp), so that it is sorted in descending order.

C + + vector usage