Question

I’m a Java developer. I’m currently learning C++. I’ve been looking at code samples for sorting. In Java, one normally gives a sorting method the container it needs to sort e.g

sort(Object[] someArray)

I’ve noticed in C++ that you pass two args, the start and end of the container. My question is that how is the actual container accessed then?

Here’s sample code taken from Wikipedia illustrating the the sort method

#include <iostream>
#include <algorithm>
#include <vector>
int main() {
 std::vector<int> vec;
 vec.push_back(10); vec.push_back(5); vec.push_back(100); 
 std::sort(vec.begin(), vec.end());
 for (int i = 0; i < vec.size(); ++i) 
     std::cout << vec[i] << ' ';
}

Answer 1

vec.begin() and vec.end() are returning iterators iterators. The iterators are kind of pointers on the elements, you can read them and modify them using iterators. That is what sort is doing using the iterators.

If it is an iterator, you can directly modify the object the iterator is referring to:

*it = X; 

The sort function does not have to know about the containers, which is the power of the iterators. By manipulating the pointers, it can sort the complete container without even knowing exactly what container it is.

You should learn about iterators (http://www.cprogramming.com/tutorial/stl/iterators.html)