There are two possible solutions: generating an adjacency matrix and then performing a breadth first search, or sorting the coordinates by x-value and y-value and performing binary search in conjunction with a breadth first search. We will be focusing on the latter solution.

Store all the obstacles and exits in two vectors: one sorted by the x-coordinates and one sorted by y-coordinates. Perform a breadth first search, using binary search to find the next obstacle/exit to the left, right, up, and down.

Time Complexity: ~\mathcal{O}(\sigma \log \sigma)~, where ~\sigma=O+E~ is the number of obstacles and exits