1.

0
2
8
3
0


2.

public class Question2 {

	public static int gap(int[] a) {
		int max = 0;
		for (int i = 0; i < a.length-1; i++) {
			int d = a[i+1]-a[i];
			if (d > max)
				max = d;
		}
		return max;
	}
	
    public static void main(String[] args) {
		int[] a = new int[args.length];
		for (int i = 0; i < a.length; i++) {
			a[i] = Integer.parseInt(args[i]);
		}
		System.out.println(gap(a));
    }
}

3.

import java.util.*;

public class DominoModel {
	private List<DominoTile> set;

	public DominoModel() {
		set = new ArrayList<DominoTile>();
		for (int i = 0; i <= 6; i++) {
			for (int j = i; j <= 6; j++) {
				set.add(new DominoTile(i,j));
			}
		}
		System.out.println(set.size());
	}

	public DominoTile pickTile() {
		if (set.size() == 0)
			return null;
		int i = (int) (Math.random()*set.size());
		return set.remove(i);
	}

	public boolean match(DominoTile tile1, DominoTile tile2) {
		return (tile1.getLeft()  == tile2.getLeft()  || 
		        tile1.getLeft()  == tile2.getRight() ||
		        tile1.getRight() == tile2.getLeft()  || 
		        tile1.getRight() == tile2.getRight());
	}
}

4.

	public static int[][] shift(int n) {
		int[][] a = new int[n][n];
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < n; j++) {
				a[i][j] = (i+j) % n;
			}
		}
		return a;
	}

5. 

   	public static boolean login(String userName, String password) {
		try {
			Scanner scanner = new Scanner(new File("accounts.txt"));
			while (scanner.hasNext()) {
				String userName1 = scanner.next();
				String password1 = scanner.next();
				
				if (userName1.equals(userName) && password1.equals(password))
					return true;
			}
			
			return false;
		} catch (FileNotFoundException e) {
			return false;
		}
	}