This is a standard shortest path problem. Use Dijkstras. Make a graph with 
edge costs based on the square's nature - Harmful or Deadly. Mark edge costs 
for Deadly as infinity. Find the cost of the shortest path. You can also use 
Bellman Ford algorithm which would be simpler to implement in this case.

Note: This problem cannot be solved with a simple BFS as the node 
exploration order as the distance from (0,0) need not correspond to the best 
way to reach that square in the graph.
eg.

. . . . . 
. * x . .
. * * * *
s * * * *

BFS will assign cost of reaching X from s as 1 (all paths considered uptil 
then to X will be passing through a harmful square). However, the best way 
to reach X is by going through the top row with cost 0.

--
DK

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