PermCheck.java

import java.util.HashSet;
import java.util.Set;

class Solution {

    private static int max(int[] A) {
        int max = A[0];
        for (int i = 1; i < A.length; i++)
            if (A[i] > max)
                max = A[i];
        return max;
    }

    public int solution(int[] A) {
        Set < Integer > setA = new HashSet < Integer > ();
        for (int i = 0; i < A.length; i++)
            setA.add(A[i]);
        return (A.length == setA.size() && this.max(A) == A.length) ? 1 : 0;
    }
}