1227. Airplane Seat Assignment Probability

`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`

1227. Airplane Seat Assignment Probability
``````struct Solution;

impl Solution {
fn nth_person_gets_nth_seat(n: i32) -> f64 {
if n > 1 {
0.5
} else {
1.0
}
}
}

#[test]
fn test() {
use assert_approx_eq::assert_approx_eq;
let n = 1;
let res = 1.0;
assert_approx_eq!(Solution::nth_person_gets_nth_seat(n), res);
let n = 2;
let res = 0.5;
assert_approx_eq!(Solution::nth_person_gets_nth_seat(n), res);
}
``````