回複：? u sure you are ok ?

The best case of course is 100 miles.
The worst case I can think of is 987miles. Maybe somebody else has a better solution. The reason i try 4 directions is that I dont know if the road is in front of me, on my back, to my left or to my right. The reason I run 1.414x100 in each direction is that in the worst case the shortest path from me to the road is between my first direction (e.g. N) and my last ditection (e.g. W). And the angle between my last try (W) and the shortest path should be less than 45 degree, otherwise on my first try I would have seen the road. So every try I only run for 100x1.414. Plus in the first three trials I need go back to my starting point (it is better to have a odometer otherwise I need set some land mark at my starting point). So within 987 mils, I am guaranteed to see the road. It is a big number unfortunately.