Test 2

1. (20%) Implement a method called determineWinner which takes two integer arrays as parameters. The arrays represent the number of points each team scored in a set of games that the teams played against each other. Your method should print out the name of the team that won the most games, or whether the tournament was a tie. Remember that if both teams score the same number of points in a game then that game is a tie (it is not a win for either team). Below is an example of how your method will be called:

   public class Tournament {
     
     public static void main(String[] args) {
       int[] a = {1, 2, 3, 4, 5, 6, 7, 8};
       int[] b = {8, 7, 6, 5, 4, 3, 2, 1};  //in game 0 a scored 1 and b scored 8 
       Tournament.determineWinner(a, b); //it was a tie
       a[0] = 10;
       Tournament.determineWinner(a, b); //a wins
       a[0] = 1;
       b[7] = 10;
       Tournament.determineWinner(a, b); //b wins
     }
   
   }
   

   Answer:

     public static void determineWinner (int [] a, int[] b) {
       int teamaLead =0; //positive is in a's favor, negative in b
       for (int i = 0; i < a.length; i++) { 
         if (a[i] > b[i]) {
           teamaLead++;
         }
         else if (a[i] < b[i]) {
           teamaLead--;
         }
       }
       if (teamaLead > 0) {
         System.out.println("Team A wins!");
       } 
       else if (teamaLead < 0) {
         System.out.println("Team B wins!");
       }
       else {
         System.out.println("It was a tie!");
       }
       
     }
   

2. (10%) What is wrong with the following program?

   public interface Talkative {
     public void talk();
     
     public String toString() {
       return "";
     }
   }
   
   public class Bobby implements Talkative {
   
     public void talk() {
       System.out.println("Hello friend!");
     }
     
     public String toString() {
       return "My name is Bobby";
     }
   
   }
   

   Answer: An interface cannot implement a method; it can only declare it.
3. (30%) What does the following program print out?

   public class A {
     private String name;
     
     public int age;
     
     protected double salary;
     
     public static int count = 0;
     
     public A() {
       age = 11;
       count++;
     }
     
     public A(String name, double salary) {
       this.name = name;
       this.salary = salary;
     }
     
     public String toString() {
       return name + " " + age + " " + salary;
     }
   
   }
   
   public class B extends A {
     
     public int score;
   
     public B(String name, double salary, int score) {
       super(name,salary);
       this.score = score;
     }
     
     public String toString(int version) {
       return version + ":" + super.toString() + " score=" + score; 
     }
     
     public static void main(String[] args) {
       A a = new A();
       System.out.println(a);
       A a2 = new A("a2", 10000);
       System.out.println(a2);
       B b = new B("b",20000,33);
       b.score = 22;
       System.out.println(b);
       B b2 = b;
       b2.score = 55;
       System.out.println(b2.toString(1));
       System.out.println(b.toString(2));
       System.out.println("count= " + b.count); 
     }
   }
   

   Answer:

   null 11 0.0
   a2 0 10000.0
   b 0 20000.0
   1:b 0 20000.0 score=55
   2:b 0 20000.0 score=55
   count= 1
   

4. (40%) Implement a method called check which takes as a parameter a two-dimensional array of integers, you can assume the array is a square of size n, and returns true if the array contains every single integer in the set 1...n^2, false otherwise. Remember that a square array of size n has exactly n^2 elements. (Yes, this is like one of the Sudoku rules).

     /**
      * Returns true if the board contains all the integers from 1...board.length^2
      * Assumes board is a square array.
      * @param board
      * @return
      */
     public static boolean check (int[][] board) {
       boolean[] isIn = new boolean[board.length * board.length]; //all false by default
       for (int rowi = 0; rowi < board.length; rowi++) {
         for (int coli = 0; coli < board.length; coli++) {
           isIn[board[rowi][coli]-1] = true;
         }
       }
       //now return true if they are all true
       for (boolean val : isIn) {
         if (!val) return false;
       }
       return true;
     }