SPOJ Problem Set (classical)
379. Ambiguous Permutations
Problem code: PERMUT2
Some programming contest problems are really tricky: not only do they
require a different output format from what you might have expected, but
also the sample output does not show the difference. For an example,
let us look at permutations.
A permutation of the integers 1 to n is an
these integers. So the natural way to represent a permutation is
to list the integers in this order. With n = 5, a
permutation might look like 2, 3, 4, 5, 1.
However, there is another possibility of representing a permutation:
You create a list of numbers where the i-th number is the
position of the integer i in the permutation.
Let us call this second
possibility an inverse permutation. The inverse permutation
for the sequence above is 5, 1, 2, 3, 4.
An ambiguous permutation is a permutation which cannot be
distinguished from its inverse permutation. The permutation 1, 4, 3, 2
for example is ambiguous, because its inverse permutation is the same.
To get rid of such annoying sample test cases, you have to write a
program which detects if a given permutation is ambiguous or not.
The input contains several test cases.
The first line of each test case contains an integer n
(1 ≤ n ≤ 100000).
Then a permutation of the integers 1 to n follows
in the next line. There is exactly one space character
between consecutive integers.
You can assume that every integer between 1 and n
appears exactly once in the permutation.
The last test case is followed by a zero.
For each test case output whether the permutation is ambiguous or not.
Adhere to the format shown in the sample output.
1 4 3 2
2 3 4 5 1
|Added by:||Adrian Kuegel|
Cube (Intel Pentium G860 3GHz)
|Languages:||All except: NODEJS PERL 6 SCM chicken VB.net |
|Resource:||own problem, used in University of Ulm Local Contest 2005|