Permutations in which n people can occupy r seats
Detailed guide and Python implementation for the 'Permutations in which n people can occupy r seats' problem.
Problem Statement
Write a function compute_nPr(n, r) that takes two non-negative integers n and r (where n >= r) and returns the number of permutations, i.e., the number of ways to arrange r items out of n items. The formula is nPr = n! / (n - r)!.
For example, if 5 people want to sit in 3 seats, the number of ways is 5P3 = 5! / 2! = 120 / 2 = 60.
- •0 <= r <= n <= 20
Examples
compute_nPr(5, 3)
60
5P3 = 5! / (5-3)! = 120 / 2 = 60.
compute_nPr(4, 2)
12
4P2 = 4! / 2! = 24 / 2 = 12.
compute_nPr(6, 6)
720
6P6 = 6! / 0! = 720 / 1 = 720.
Need a Hint?
Edge Cases to Watch
- Empty input structures
- Single element inputs
- Large numerical bounds
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