STL——vector

参考自CPP标准文档vector

一、定义

Vectors are sequence containers representing arrays that can change in size

特点：

1.  Sequence

    Elements in sequence containers are ordered in a strict linear sequence. Individual elements are accessed by their position in this sequence.

2. Dynamic array

    Allows direct access to any element in the sequence, even through pointer arithmetics（算数：加减乘除）, and provides relatively fast addition/removal of elements at the end of the sequence.

3. Allocator-aware

    The container uses an allocator object to dynamically handle its storage needs

初始化

// constructors used in the same order as described above:  std::vector<int> first;                                // empty vector of ints  std::vector<int> second (4,100);                       // four ints with value 100  std::vector<int> third (second.begin(),second.end());  // iterating through second  std::vector<int> fourth (third);                       // a copy of third  // the iterator constructor can also be used to construct from arrays:  int myints[] = {16,2,77,29};  std::vector<int> fifth (myints, myints + sizeof(myints) / sizeof(int) );

 vector 的data成员，返回指向数组的首地址，因为vector是线性连续存储的，所以可以通过指针的偏移访问vector的元素。

#include <iostream>#include <vector>int main (){  std::vector<int> myvector (5);  int* p = myvector.data();  *p = 10;  ++p;  *p = 20;  p[2] = 100;  std::cout << "myvector contains:";  for (unsigned i=0; i<myvector.size(); ++i)    std::cout << ' ' << myvector[i];  std::cout << '\n';  return 0;}

Output：

myvector contains: 10 20 0 100 0

swap

vector的交换大小可以不一样，同array不同（array的size必须一样才可以交换）

使用区别：

1、如果你需要高效的随机存取（即[]操作），不在乎插入和删除的效率，应该使用vector

2.  如果你需要大量的插入和删除，不关心随机存取，应该使用list

3. 如果你需要随机存取，而且关心数据的插入删除，应该使用deque