Interview Questions with diamond

It is known that one has 10 floors and each layer has a diamond

1. You are in an elevator. The elevator goes up, stops every floor only once, and then goes to the upper floor.

2. You can only get one diamond at a time. (You cannot exchange diamond !), Of course, you can observe the diamond on each layer.

Question

How to maximize the probability of "getting the biggest diamond"

Assume that the largest diamond is D10, and the smallest diamond is D1.

1. Assume that only the floors behind the first floor are taken away if they are larger than the first floor.

2. Assume that you only observe the largest diamond in the first two layers, and take the diamond from the back of the floor as long as it is larger than the largest diamond in the first two layers,

What is the highest probability?