hw0: https://sp21.datastructur.es/materials/hw/hw0/hw0
hw0简单介绍了Java的基本语法，与python等其他语言的对比，了解java基础可以跳过。

• Creative Exercise 1a: Drawing a Triangle
• Creative Exercise 1b: DrawTriangle
• Exercise 2
• Exercise 3
• Exercise 4

Creative Exercise 1a: Drawing a Triangle

public class Ex1a {
    public static void main(String[] args) {
        Draw(5);
    }

    public static void Draw(int x) {
        int y = 1;
        while (y <= x) {
            int i = 0;
            while (i < y) {
                System.out.print('*');
                i++;
            }
            System.out.println();
            y++;
        }
    }
}

Creative Exercise 1b: DrawTriangle

public class Ex1b {
    public static void main(String[] args) {
        drawTriangle(10);
    }

    public static void drawTriangle(int N) {
        int x = 1;
        while (x <= N) {
            int i = 0;
            while (i < x) {
                System.out.print('*');
                i++;
            }
            System.out.println();
            x++;
        }
    }
}

Exercise 2

public class Ex2 {
    /** Returns the maximum value from m. */
    public static int max(int[] m) {
        int maxNumber = 0;
        int i = 0;
        while (i < m.length) {
            if (maxNumber < m[i]) {
                maxNumber = m[i];
            }
            i++;
        }
        return maxNumber;
    }
    public static void main(String[] args) {
        int[] numbers = new int[]{9, 2, 15, 2, 22, 10, 6};
        System.out.println(max(numbers));
    }
}

Exercise 3

public class Ex3 {
    /** Returns the maximum value from m using a for loop. */
    public static int max(int[] m) {
        int maxNumber = 0;

        for (int i = 0; i < m.length; i++) {
            if (maxNumber < m[i]) {
                maxNumber = m[i];
            }
        }
        return maxNumber;
    }
    public static void main(String[] args) {
        int[] numbers = new int[]{9, 2, 15, 2, 22, 10, 6};
        System.out.println(max(numbers));
    }
}

Exercise 4

public class Ex4 {
    public static void windowPosSum(int[] a, int n) {
        /** your code here */
        for (int i = 0; i < a.length; i++) {
            if (a[i] < 0) {
                continue;
            }
            if (i == a.length - 1) {
                break;
            }
            for (int j = 1; j <= n; j++) {
                if (i + j >= a.length){
                    break;
                }
                a[i] = a[i] + a[i + j];
            }
        }
    }

    public static void main(String[] args) {
        int[] a = {1, 2, -3, 4, 5, 4};
        int n = 3;
        windowPosSum(a, n);

        // Should print 4, 8, -3, 13, 9, 4
        System.out.println(java.util.Arrays.toString(a));
    }
}