I have a polygon, it has five points like this:
![enter image description here](https://i.stack.imgur.com/qO02u.png)

then I add another point to polygon (the red one):
![enter image description here](https://i.stack.imgur.com/iGoAp.png)

what's the algorithm to determine two polygons is same one (not just angle/length is same, coordinates also same too).