import java.util.*;
import java.lang.*;
import java.io.*;
 
class Ideone {
    public static boolean isContiguous(long[] array) {
        Set <Long> hashset = new HashSet <Long> ();
        long min = array[0];
        long max = array[0];
        for (int i = 0; i < array.length; i++) {
            if (hashset.add(array[i]) == false) return false;
            if (min > array[i]) min = array[i];
            if (max < array[i]) max = array[i];
        }
        return max - min + 1 == array.length;
    }
    public static void main(String[] args) throws java.lang.Exception {
        System.out.println(isContiguous(new long[] { 1, 2, 3, 5, 6, 7 }));    // false, missing 4
        System.out.println(isContiguous(new long[] { 1, 2, 3, 4, 4, 6, 7 })); // false, missing 5
        System.out.println(isContiguous(new long[] { 1, 2, 3, 5, 6, 7, 4 })); // true
    }
}

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