Codility Test (07. PermCheck)

Codility Test (07. PermCheck)

A non-empty array A consisting of N integers is given.

A permutation is a sequence containing each element from 1 to N once, and only once.

For example, array A such that:

A[0] = 4
A[1] = 1
A[2] = 3
A[3] = 2 is a permutation, but array A such that:

A[0] = 4
A[1] = 1
A[2] = 3 is not a permutation, because value 2 is missing.

The goal is to check whether array A is a permutation.

Write a function:

class Solution { public int solution(int[] A); }

that, given an array A, returns 1 if array A is a permutation and 0 if it is not.

For example, given array A such that:

A[0] = 4
A[1] = 1
A[2] = 3
A[3] = 2 the function should return 1.

Given array A such that:

A[0] = 4
A[1] = 1
A[2] = 3 the function should return 0.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [1..100,000]; each element of array A is an integer within the range [1..1,000,000,000]. Copyright 2009–2019 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.

問題回答

import java.util.*;

class Solution {
    public int solution(int[] A) {
        // write your code in Java SE 8
        Arrays.sort(A);
        for(int i = 0; i < A.length; i++) {
            if(A[i] != i + 1) {
                return 0;
            }
        }
        return 1;
    }
}