Please solve the programming task below using a self-contained code snippet in a markdown code block.

You are given an integer array heights representing the heights of buildings, some bricks, and some ladders.
You start your journey from building 0 and move to the next building by possibly using bricks or ladders.
While moving from building i to building i+1 (0-indexed),

If the current building's height is greater than or equal to the next building's height, you do not need a ladder or bricks.
If the current building's height is less than the next building's height, you can either use one ladder or (h[i+1] - h[i]) bricks.

Return the furthest building index (0-indexed) you can reach if you use the given ladders and bricks optimally.
 
Please complete the following python code precisely:
```python
class Solution:
    def furthestBuilding(self, heights: List[int], bricks: int, ladders: int) -> int:
```