You are chasing a mouse living in a row of eight houses. Every night the mouse moves from the house it is in, to an adjacent house, and stays there the whole day. Apart from this, you have no a-priori information on the mouse's locations nor on its movements. However, you do have two mousetraps available. If you leave a mousetrap for the full day in a house, you are guaranteed to catch the mouse if on that day it happens to have targeted that particular house.
You are contemplating the mousetrap placement strategy to follow, and land on the conclusion that if on subsequent days you place the mousetraps in houses 1-2, 2-3, ..., 7-8, you are certain to catch the mouse in no more than 7 days.
Can you do better? What is the shortest time in which you can be guaranteed of catching the mouse?