1227. Airplane Seat Assignment Probability

https://leetcode.com/problems/airplane-seat-assignment-probability

Description

n passengers board an airplane with exactly n seats. The first passenger has lost the ticket and picks a seat randomly. But after that, the rest of passengers will:

• Take their own seat if it is still available,

• Pick other seats randomly when they find their seat occupied

What is the probability that the n-th person can get his own seat?

Example 1:

**Input:** n = 1
**Output:** 1.00000
**Explanation:** The first person can only get the first seat.

Example 2:

**Input:** n = 2
**Output:** 0.50000
**Explanation:** The second person has a probability of 0.5 to get the second seat (when first person gets the first seat).

Constraints:

• 1 <= n <= 10^5

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