c++ STL之vector

1.new

vector<int> V;

2.push a element to V

V.push_back(element);

3.visit elements in V

• by index

  cout << V[i];

• by iterator
  iterator is analogous to pointer,the definer is:

  vector<typename>::iterator it;

  then 'it' is a variable,the type is 'vector<typename>::iterator',we can get the address of the element via *it

• eg:

  vector<int>::iterator it = V.begin();
  for(int i=0; i<V.size(); i++){
      cout << *(it + i);
  }

  Note:V[ i ] is equal to *(V.begin() + i);

4.begin() and end()

• begin() gain address of the V's first element,and end() gain next address of the V's last element,usually as the flag of the iterator's tail

• eg:

  //vector's iterator can only utilize like this:
  for(vector<int>::iterator it = V.begin(); it != V.end(); it++)//V[i].begin is equal to V[0]
      cout << *it;

5.pop_back()

• delete last element

  V.pop_back();

6.size()

• return unsigned type

7.clear()

• O(n)

  V.clear()// V.clear() is equal to V.erase(V.begin(),V.end())

8.insert()

• insert(it,x), time complexity is O(n)

  V.insert(V.begin() + m,value);

9.erase()

• delele single element

  V.erase(V.begin() + m);//m is index

• delete all elements in a range:[m, k)

  V.erase(V.begin() + m,V.begin() + k);