Insight · ★★★★☆ · ~8 min
Catching the Submarine
A submarine on an integer line, unknown start + speed. Can you always hit it?
by MindYourPuzzle
A submarine moves along a number line starting at an unknown integer position, moving +1 or -1 each step (unknown direction, constant). You can only test one integer position per turn.
Can you guarantee catching it in finite time?
Hints