C + + vector base __c++

Vector is a very useful container in C + +, and here's a summary of the container. 1 Basic Operations

(1) header file #include<vector>.

(2) Declaration and initialization of vector variables

  Vector<int> A;                                declares an int-type vector a
  vector<int> a (a);                            Declares a vector with an initial size of 10
  vector<int> A (1);                         Declares a vector
  vector<int> B (a) with an initial size of 10 and an initial value of 1;                             Declares and uses vector A to initialize vector b
  vector<int> B (A.begin (), A.begin () +3);        The initial value of vector b from the No. 0 to 2nd (total 3) in a vector

In addition, you can initialize vectors directly by using arrays:

  int n[] = {1, 2, 3, 4, 5};
  Vector<int> A (n, n+5);              The first 5 elements of the array n are used as the initial value of vector a
  (vector<int> a (&n[1], &n[4]);        To use an element within the n[1]-n[4] range as the initial value of a vector a

(3) Tail Insert number: Vec.push_back (a);

(4) Use subscript to access elements,cout<<vec[0]<<endl; remember that subscripts start at 0.

(5) Accessing elements using iterators.

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 i+1 element;

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

Vec.erase (Vec.begin () +i,vec.begin () +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 structural body, but note: The structure is defined as global, otherwise there will be errors. 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 structural, you can define comparison functions within the structure, sorted by Id,length,width ascending order.
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 flip the element: Requires a header file #include<algorithm>

Reverse (Vec.begin (), Vec.end ()); Flip the element (in vector, if two iterators are required in a function, the latter does not normally contain.)

(2) Use sort order: Need header file #include<algorithm>,

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

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

To define a sort comparison function:

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