Problem
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 the passengers will:
Take their own seat if it is still available, and
Pick other seats randomly when they find their seat occupied
Return **the probability that the *nth* person gets 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
Solution (Java)
class Solution {
public double nthPersonGetsNthSeat(int n) {
if (n == 1) {
return 1.0D;
}
return 0.5D;
}
}
Explain:
nope.
Complexity:
- Time complexity : O(n).
- Space complexity : O(n).