Iterator in Standard Template Library

紀錄一下STL裡面常用的幾種iterator

reverse_iterator

顧名思義就是將容器從後面往前的順序訪問。

#include <iterator>
#include <iostream>
using namespace std;
int main()
{
	char array[] = "abcde";
	using backword_iterator = reverse_iterator < char * > ;
	backword_iterator it = backword_iterator(array + 5);
	backword_iterator itend = backword_iterator(array);
	while (it != itend)
		cout << *it++;
	cout << endl;
}

insert_iterator

共分三種

• back_inserter 插入在容器最尾端，需要Container有push_back功能，所以只支援vector deque list
• front_inserter 插入在容器最前端，需要Container有push_front功能，所以之支援deque list
• insert_iterator 可插入在任何容器的任何位置，需要Contaner有insert功能，所有Container都支援。

#include <iterator>
#include <iostream>
#include <list>
using namespace std;
template <typename T>
void printContainer(const list<T>& lists)
{
	for (auto iter = begin(lists); iter != end(lists); ++iter)
		cout << *iter;
	cout << endl;
}
template <typename T>
insert_iterator<T> make_insert_iterater(T& lists, typename T::iterator iter)
{
	return insert_iterator<T>(lists, iter);
}
int main()
{
	int array[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
	list<int> integers;
	copy(array + 5, array + 10, back_inserter(integers));
	printContainer(integers);
	using backword_iterator = reverse_iterator < int * >;
	copy(backword_iterator(array + 5), backword_iterator(array), front_inserter(integers));
	printContainer(integers);
	list<int>::iterator iter = integers.begin();
	iter++; iter++;
	copy(array + 1, array + 3, make_insert_iterater(integers, iter));
	printContainer(integers);
}

move_iterator

C++11之後新增的，顧名思義就是加上move semantics，給個範例就很明顯了。

#include <iostream>     // std::cout
#include <iterator>     // std::move_iterator
#include <vector>       // std::vector
#include <string>       // std::string
#include <algorithm>    // std::copy

int main() {
	std::vector<std::string> foo(3);
	std::vector<std::string> bar{ "one", "two", "three" };

	typedef std::vector<std::string>::iterator Iter;

	std::copy(std::move_iterator<Iter>(bar.begin()),
		std::move_iterator<Iter>(bar.end()),
		foo.begin());

	// bar now contains unspecified values; clear it:
	bar.clear();

	std::cout << "foo:";
	for (std::string& x : foo) std::cout << ' ' << x;
	std::cout << '\n';

	return 0;
}