This theme implements a built-in Jekyll feature, the use of Rouge, for syntax highlighting. It supports more than 100 languages. This example is in C++. All you have to do is wrap your code in a liquid tag:
{% highlight c++ linenos %}
code code code
{% endhighlight %}
The keyword linenos
triggers display of line numbers.
Produces something like this:
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int main(int argc, char const \*argv[])
{
string myString;
cout << "input a string: ";
getline(cin, myString);
int length = myString.length();
char charArray = new char * [length];
charArray = myString;
for(int i = 0; i < length; ++i){
cout << charArray[i] << " ";
}
return 0;
}