In an alternating permutation of numbers 1 to n, the numbers are arranged so that they alternately increase and decrease. For example, there are five alternating permutations of the numbers 1, 2, 3, and 4:
1 3 2 4
1 4 2 3
2 3 1 4
2 4 1 3
3 4 1 2
Write a function to count the alternating permutations for a set of n numbers.
Solution Stats
Problem Comments
3 Comments
Solution Comments
Show comments
Loading...
Problem Recent Solvers10
Suggested Problems
-
3433 Solvers
-
Magic is simple (for beginners)
11167 Solvers
-
Factorions: Numbers that equal the sum of the factorials of their digits
83 Solvers
-
560 Solvers
-
compress sequence into intervals
98 Solvers
More from this Author322
Problem Tags
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
The test case result for n=5 seems a tad high.
Tim, that last case is altperm(altperm(5)). I did that to discourage lookup solutions.
Oops--my mistake.