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java-intermediate_exercises.md

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Intermediate Level Exercises

1 FizzBuzz

Create a method that takes in an integer number n and prints out a count from 0 to n with the following rules applied:

  1. Numbers divisible by 3: print Fizz
  2. Numbers divisible by 5: print Buzz
  3. Numbers divisible by 3 and 5: print FizzBuzz

Method definition should take the form:

public static void fizz_buzz(int n)
{
    // TODO Your code here
}

Example output for the function:

1
2
Fizz
4
Buzz
Fizz
7
8
Fizz
Buzz
11
Fizz
13
14
FizzBuzz
16

2 Merge Two Lists

Create a function zip that takes in two sorted arrays list1 and list2 and returns as an output both arrays merged together in order. You can assume that list1 and list2 are already sorted in accending order.

Function definition should take the form:

public static int[] zip(int[] list1, int[] list2)
{
    // TODO your code here
}

Example output for the function:

int[] list1 = {1,3,4,7,9,18};
int[] list2 = {2,4,6,8,10};
int[] listOut = zip(list1, list2);
for(int i: listOut)
{
   System.out.print(i + " ");
}

>>> 1 2 3 4 4 6 7 8 9 10 18           ## Note that numbers that appear in both lists are repeated

3 Squared Distance

Create a function that takes in two points as tuples and returns the euclidean distance between them. At first just find the distance between two points with only two dimensions so that the tuples look like: (x1, y1) and (x2, y2). Then try and extend your code to work for tuples of all sizes.

Function definition should take the form:

public static Vector dist(Vector point1, Vector point2)
{
    // TODO Your code here
}

Where a vector is the following class:

public class Vector
{
    private double[] v;

    /** Constructor 
     *  create and n-dimensional vector by passing in numbers seperated by commas example: 
     *  Vector v = new Vector(1, 2, 3, 4); 
     */
    public Vector(double... v)
    {
        this.v = new double[v.length];
        for (int i = 0; i < v.length; i++)
        {
            this.v[i] = v[i];
        }
    }

    /** Returns the number of dimensions in the vector */
    public int dims()
    {
        return v.length;
    }

    /** Gets the value at index `i` for the vector */
    public double get(int i)
    {
        if (i >= v.length)
            throw new RuntimeException("Cannot access dim " + i + " in vector length " + v.length);
        return v[i];
    }
}

Example output for the function:

Vector point1 = new Vector(0, 10);
Vector point2 = new Vector(0, 20);
double d = dist(point1, point2);
System.out.println(d);

>>> 10.0

Or for a more complex example

Vector point1 = new Vector(5, 10, 13);
Vector point2 = new Vector(7, 20, 18);
double d = dist(point1, point2);
System.out.println(d);

>>> 11.3578

4 Palindrome

Write a function that, given a string, checks whether the string is a palindrome (same forwards as backwards) and returns true or false if it is, or isn't, respectively.

public static boolean isPalindrome(String s)
{
   // TODO Your code here
}

Example output for the function:

isPalindrome("hello world");
>>> false

isPalindrome("bob");
>>> true

isPalindrome("a man a plan a canal panama");
>>> true

5 Brackets

Write a method that takes in a string and checks if any brackets within the string are both opened and closed in order. Valid brackets are round (, ) curly {, } and square [, ]. If a bracket is opened, the next closing bracket must match it. Nesting sets of brackets are possible, for example a valid set of brackets is: {} () (()) ({[]}). Invalid options are: non-matching pairs i.e. [) or closing brackets before opening brackets ][ )( or unclosed brackets ([{(. All other characters and whitespace should be ignored.

public static boolen validBrackets(String s)
{
    // TODO Your code here
}

Example output for the function:

>>> valid_brackets("int[] list = {1, 2, 3, 4};  System.out.println(\"hello world!\");")
True

>>> valid_brackets("int[] list = 1, 2, 3, 4};")             # missing opening bracket
False

>>> valid_brackets("System.out.println(\"hello world!\" ")  # missing closing bracket
False

>>> valid_brackets("int[] list = {1, 2, 3, 4];")            # missmatched bracket pair
False

>>> valid_brackets("if(false == true")                      # unclosed bracket
False

5 Roman Numerals

Write a function that takes in a set of Roman Numerals as a string and outputs the correct Arabic number as an integer. Use the following guide:

Symbol | Value
-------|------------
  I    |   1
  V    |   5
  X    |   10
  L    |   50
  C    |   100
  D    |   500
  M    |   1000

And example function definition:

public static  int roman2Decimal(String numeral)
{
    // Your code here
}

Assume that Roman Numerals are always in decending order for addition, (so VI = 5 + 1 = 5) and in acending order for subtraction (so IV = 5 - 1 = 4) to make the numbers not included in the numerals list.

Examples:

roman2Decimal("MI");
>>> 1001
roman2Decimal("XIV");
>>> 14
roman2Decimal("MCMXCIV");
>>> 1994

6 Line Intersection

Write a function that takes in Vectors (from the class given above) that represent coordinates on an x-y plane (x1,y1),(x2,y2),(x3,y3),(x4,y4) where the first two coordinates are the line A - B and the second two are the line C - D. Return a boolean value of True if the lines AB and CD intersect, and a False if they don't. Hint: https://en.wikipedia.org/wiki/Line%E2%80%93line_intersection

public static boolean intersect(Vector a, Vector b, Vector c, Vector d)
{
   // TODO Your code here
}

Example output for the function:

Vector a = (10, 0);
Vector b = (10, 20);
Vector c = (0, 10);
Vector d = (30, 10);
intersect(a, b, c, d);

>>> true

False example:

Vector a = (0, 0);
Vector b = (0, 10);
Vector c = (10, 10);
Vector d = (30, 30);
intersect(a, b, c, d);

>>> false