C++ vector::push_back 用法剖析

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C++编程语言中有一种叫做Vector的应用方法，它的作用在实际编程中是非常重要的。下面介绍一下C++ Vector的相关应用技巧及基本内容，希望能给大家带来一些帮助。

(1)vector< 类型 > 标识符 ;

(2)vector< 类型 > 标识符(最大容量) ；

(3)vector< 类型 > 标识符（最大容量，初始所有值）；

(4) int i[4] = {12,3,4,5};

vector< 类型 > vi(i , i+2); //得到i索引值为3以后的值 ；

(5)vector< vector<int> > //vi 定义2维的容器；记得一定要有空格，不然会报错

vector< int > line
// 在使用的时候一定要首先将vi个行进行初始化;
for(int i = 0 ; i < 10 ; i ++)
{
vector.push_back(line);
}

个人认为使用vector定义二维数组很好，因为长度可以不预先确定。很好！

(6)C++ Vector排序

vector< int > vi ;   
vi.push_back(1);  
vi.push_back(3);  
vi.push_back(0);  
sort(vi.begin() , vi.end()); /// /从小到大  
reverse(vi.begin(),vi.end()) /// 从大到小

(7)顺序访问

vector < int > vi ;
for( int i = 0 ; i < 10 ; i ++)
{
vi.push_back(i);
}
for(int i = 0 ; i < 10 ; i ++) /// 第一种调用方法
{
cout <<vi[i] <<" " ;
}
for(vector<int>::iterator it = vi.begin() ;it !=vi.end() ; it++) ///第二种调用方法
{
cout << *it << " " ;
}

(8)寻找

vector < int > vi ;   
for( int i = 0 ; i < 10 ; i ++)  
{  
vector.push_back(i);  
}   
vector < int >::interator it = find(vi.begin() , vi.end,3) ;  
cout << *it << endl ; ///返回容器内找到值的位置。

(9)使用数组对C++ Vector进行初始化

int i[10] ={1,2,3,4,5,6,7,78,8} ;
///第一种
vector<int> vi(i+1,i+3); ///从第2个元素到第3个元素
for(vector <int>::interator it = vi.begin() ; it != vi.end() ; it++)
{
cout << *it <<" " ;
}

(10) 结构体类型

struct temp  
{  
  public :  
  string str ;   
  public :  
  int id ;  
}tmp;
int main()  
{  
vector <temp> t ;   
temp w1 ;   
w1.str = "Hello world" ;  
w1.id = 1 ;   
t.push_back(t1);  
cout << w1.str << "," <<w1.id <<endl ;   
return 0 ;   
}

C++ Vector的基本内容就为大家介绍到这里。

vector::push_back

public member function

void push_back ( const T& x );

Add element at the end

Adds a new element at the end of the vector, after its current last element. The content of this new element is initialized to a copy ofx.

This effectively increases the vector size by one, which causes a reallocation of the internal allocated storage if the vector size was equal to the vector capacity before the call. Reallocations invalidate all previously obtained iterators, references and pointers.

Parameters

x: Value to be copied to the new element.
T is the first template parameter (the type of the elements stored in the vector).

Return value

none

If a reallocation happens, it is performed using Allocator::allocate(), which may throw exceptions (for the defaultallocator,bad_alloc is thrown if the allocation request does not succeed).

Example

// vector::push_back#include <iostream>#include <vector>int main (){  std::vector<int> myvector;  int myint;  std::cout << "Please enter some integers (enter 0 to end):\n";  do {    std::cin >> myint;    myvector.push_back (myint);  } while (myint);  std::cout << "myvector stores " << int(myvector.size()) << " numbers.\n";  return 0;}

The example uses push_back to add a new element to the vector each time a new integer is read.

Complexity

Constant (amortized time, reallocation may happe

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