STL Learning Notes (iterator adapter)

Reverse (reverse) iterator

The reverse iterator is a mating adapter. Redefine the increment and decrement operations. So that it behaves just upside down.

If you use such iterators, the algorithm will process the elements in reverse order. All standard containers allow the use of reverse iterators to traverse elements. Here's an example:

1#include <iostream>2#include <list>3#include <algorithm>4 using namespacestd;5 6 voidPrintintelem)7 {8cout<<elem<<' ';9 }Ten  One intMain () A { -list<int>Coll; -      for(intI=1; i<=9;++i) the Coll.push_back (i); - For_each (Coll.begin (), Coll.end (), print); -cout<<Endl; - For_each (Coll.rbegin (), Coll.rend (), print); +cout<<Endl; -}

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Insert (placement) iterator

With this iterator, the algorithm can perform the placement behavior rather than the overwrite behavior. It provides the following actions

The C + + standard library provides three types of insert iterators: Back inserters, front inserters, General inserters. The difference between them is the insertion position.

In fact, they each call different member functions in the owning container.

Obviously, the container itself must support the function called by the Insert iterator, otherwise the insert iterator will not be available.

The following shows the use of the back inserters

1#include <iostream>2#include <vector>3#include <algorithm>4#include"Print.cpp"5 using namespacestd;6 7 intMain ()8 {9vector<int>Coll;Tenback_insert_iterator<vector<int> >ITER (coll); One*iter=1; Aiter++; -*iter=2; -iter++; the*iter=3; - Print_elements (coll); -Back_inserter (coll) = -; -Back_inserter (coll) = -; + Print_elements (coll); -Coll.reserve (2*coll.size ()); + copy (Coll.begin (), Coll.end (), Back_inserter (coll)); A Print_elements (coll); at}

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Stream (Stream) iterator

We can use stream iterators as the origin and starting point for the algorithm.

A IStream iterator can be used to read elements from the input stream, and an ostream iterator can be used to write elements to the output stream.

1.Ostream iterators

The Ostream iterator can write the assigned value to the output stream. As a result, the algorithm can use a generic iterator interface to perform scribble actions directly on the stream. The individual action functions of the Ostream iterator are listed below.

The following shows the use of the Ostream iterator

1#include <iostream>2#include <vector>3#include <algorithm>4#include <iterator>5 using namespacestd;6 7 intMain ()8 {9ostream_iterator<int> Intwriter (cout,"\ n");Ten*intwriter= the; Oneintwriter++; A*intwriter= the; -intwriter++; -*intwriter=-5; thevector<int>Coll; -      for(intI=1; i<=9;++i) - Coll.push_back (i); -Copy (Coll.begin (), Coll.end (),ostream_iterator<int>(cout)); +cout<<Endl; -Copy (Coll.begin (), Coll.end (),ostream_iterator<int> (cout,"<")); +cout<<Endl; A}

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2.istream iterators

The IStream iterator is used to read elements from the input stream. Through the IStream iterator, the algorithm can read data directly from the stream.

Here are the various operation functions of the IStream iterator

The following shows the actions of the IStream iterator

1#include <iostream>2#include <iterator>3 using namespacestd;4 5 intMain ()6 {7istream_iterator<int>Intreader (CIN);8istream_iterator<int>intreadereof;9      while(intreader!=intreadereof)Ten     { Onecout<<"once:"<<*intReader<<Endl; Acout<<"once again:"<<*intReader<<Endl; -++Intreader; -     } the}

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STL Learning Notes (iterator adapter)