#include <iostream>
#include <cstdlib>
#include <vector>
using namespace std;

int main()
{
	int a[] = {10, 20, 30, 40, 50};
	size_t n = sizeof a / sizeof a[0];           //n is 5

	int *p1 = a;                                 //point to the 10
	int *p2 = a + 4;                             //point to the 50
	ptrdiff_t d1 = p2 - p1;                      //d1 is 4
	p1 += d1;                                    //Now p1 points to the 50.

	vector<int> v(a, a + n);
	vector<int>::size_type s = v.size();         //s is 5

	vector<int>::iterator it1 = v.begin();       //refer to the 10
	vector<int>::iterator it2 = v.begin() + 4;   //refer to the 50
	vector<int>::difference_type d2 = it2 - it1; //d2 is 4
	it1 += d2;                                   //Now it1 refers to the 50.

	return EXIT_SUCCESS;
}