Hint: Binary search on the answer.
Hint: We are given that there are at most 1000 top sticks.
2318 TOYS (3)
Hint: For each toy, find the leftmost cardboard (using binary search) that lies to the right of the toy.
Hint: Each obstacle induces a ‘‘shadow.’’
1696 Space Ant (4)
Hint: Given the current point and the previous point, find how to find the next point just by using ccw.
Hint: Intersection of half-planes.
1408 Fishnet (7)
3525 Most Distant Point from the Sea (8, challenge problem)
Hint: Binary seaerch on the answer.
3246 Game (9, challenge problem)
3266 Cow School (10, challenge problem)
Note: This is an extremely hard problem. If you can't figure out why this is a geometry problem, don't even start coding.