几种类型的for循环

//win10下，VS2017中编译
#include <iostream>
using std::cout;
using std::endl;
#include <vector>
using std::vector;
int main()
{
	int a[] = { 2,3,5,7 };//整型数组
	vector<int> v = { 6,8,5,1,7 };//vector容器，直接初始化

	//方式一,下标
	for (int i = 0; i < 4; ++i)
	{
		cout << a[i] << "\t";
	}
	cout << endl;

	for (int i = 0; i < v.size(); ++i)
	{
		cout << v[i] << "\t";
	}
	cout << endl;
	

	//方式二,迭代器,类似于指针
	for (vector<int>::iterator it = v.begin(); it != v.end(); ++it)
	{
		cout << *it << "\t";
	}
	cout << endl;

	//用auto改写,auto自动推导类型
/*	for (auto i = 0; i < 4; ++i)
	{
		cout << a[i] << "\t";
	}
	cout << endl;

	for (auto it = v.begin(); it != v.end(); ++it)
	{
		cout << *it << "\t";
	}
	cout << endl;
*/


	//方式三，C++11/14引入 :(本质上是迭代器实现)
	for (const auto& x : a)
	{
		cout << x << "\t";
	}
	cout << endl;

	for (auto& x : v)
	{
		cout << x << "\t";
	}
	cout << endl;

	
	//方式四，BOOST_FOREACH,不仅支持数组、容器，还支持迭代器的pair和逆序遍历
	//#include "boost/foreach.hpp"
/*	BOOST_FOREACH(auto& x, v)
	{
		cout << x << "\t";
	}
*/
    return 0;
}