I am developing a little game, where I need an A* path-finding algorithm for enemies who follow the player. I have already learned and tested a path-finding algorithm, but it only works with fixed-size array.

How can I turn an open world into a fixed-size array? I am developing with Irrlicht engine 1.6 version. I know that it is a quite old, but it is the only engine which works for me, on Windows XP.

Here is my A star path-finding code that works on a 2D grid. Additionally , if needed, Here there is a link to a walking person I have created with Irrlicht. You must place the media folder in your local drive.