Selection Sort in C++
Style

At the moment, this is C with iostream. The style obliterates the point in using C++ at all.

Code Review


Almost complete absence of standard library

The code does not leverage the functionality standard library provides. On top of that, the code is not better in any ways than standard library functionality
Using int for size of objects in memory

Indexable memory is very big nowadays. int is guaranteed to be only 16 bits, so it might not be enough to index all of the available memory on the system. Use std::size_t for that.
C style swapping

C++ has std::swap() located in &lt;utility&gt;. It will probably be as good as your version, if not better (it might invoke some assembly).
Using std::endl

std::endl does not only put a newline, but also flushes the buffer. Flushing is a very expensive operation, and can hinder performance of the code in tight loops.


What is done right


No using namespace std

This is good step forward. Do not use it, in any IDE/text editor code highlighting and completion will be available, if not, find a plugin for your text editor. By grabbing everything in std, you will overwhelm the ability of the IDE/text editor to give you real-time code completion suggestions.
Uniform initialization

Using uniform initialization avoids all of the vexing parse issues. Do note though, that sometimes they might invoke std::initializer_list constructor, which might not be what you need.


tl;dr

Use Standard library. Use concepts and idioms. Any decent C++ programmer knows that to reimplement standard library one must have a very good reason to do so.