adding the iterator implementation code

lectures/10_linked_lists/vec_main.cpp

@@ -0,0 +1,33 @@
+#include <iostream>
+//#include <vector>
+#include "vec.h"
+
+int main(){
+	vec<std::string> teams;
+	teams.push_back("rpi");
+	teams.push_back("wpi");
+	teams.push_back("yale");
+	teams.push_back("brown");
+	teams.push_back("cornell");
+	teams.push_back("colgate");
+	teams.push_back("miami");
+	teams.push_back("colorado");
+	teams.push_back("harvard");
+	std::cout << "==== teams ==== " << std::endl;
+	int size = teams.size();
+	for(int i=0; i<size; ++i){
+		std::cout << teams[i] << std::endl;
+	}
+
+	// this line calls the other constructor.
+	vec<double> v(4, 0.0);
+	v[0] = 13.1; v[2] = 3.14;
+
+	vec<double>::iterator itr = v.begin();
+	std::cout << "the first element of v is: " << *itr << std::endl;
+	std::cout << "printing elements in v: " << std::endl;
+	while(itr != v.end()){
+		std::cout << "print " << *itr << std::endl;
+		++itr;
+	}
+}