URI Online Judge Solution 1663 in java | Ambiguous Permutations

URI Online Judge | 1663

Ambiguous Permutations

Local Contest, University of Ulm  Germany

Timelimit: 5

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 ordering of 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.

Input

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.

Output

For each test case output whether the permutation is ambiguous or not. Adhere to the format shown in the sample output.

Sample Input	Sample Output
4 1 4 3 2 5 2 3 4 5 1 1 1 0	ambiguous not ambiguous ambiguous

Univeristy of Ulm Local Contest 2005/2006

URI Online Judge Solution 1663 in java | Ambiguous Permutations:

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {

        Scanner in = new Scanner(System.in);

        int[] arr = new int[1000005];

        int[] inv = new int[1000005];

        int n, cnt;

        n = in.nextInt();

        while(true) {

            if(n == 0) {

                break;

            }

            cnt = 0;

            for (int i = 1; i <= n; i++) {

                arr[i] = in.nextInt();

                inv[arr[i]] = i;

            }

            for (int i = 1; i <= n; i++) {

                if(arr[i] == inv[i]) {

                    cnt++;

                }

            }

            if(cnt == n) System.out.println("ambiguous");

            else System.out.println("not ambiguous");

            n = in.nextInt();

        }

    }

}