Solutions to CompSci 6 Test 1 Spring 2006

 1. 
 A. Not Equivalent. If value=8 and other=3 then A prints ok twice,
 the first code segment prints it once.

 B. Not Equivalent. If value=8 and other=5, then B prints ok,
 the first code segment doesn't print anything.

 C. Equivalent

 D. Equivalent


 2.
 A. int

 B. two, count and dig

 C. 3

 D. 0

 E. Returns the number of times "value" appears in "number", where
 value is a digit from 1-9.


 3.
 A. House

 B. getAddress()

 C. myNumberOfBedrooms is private, the BeachHouse class cannot access it.

 D. Make myNumberOfBedrooms protected, then the subclass BeachHouse
 can access this state.


4. 
   public ArrayList<String> equalize(ArrayList<String> schools)
   {
      int dukecount = 0;
      int unccount = 0;
      
      for (String current: schools)
      {
            if (current.equals("duke"))
               dukecount++;
            if (current.equals("unc"))
               unccount++;
       }
        while (dukecount < unccount)
        {
           schools.add("duke");
           dukecount++;
        }
        while (unccount < dukecount)
        {
           schools.add("unc");
           unccount++;
        }
        return schools;
   }




5.
A.
   // returns a String equivalent to phrase with all occurrences of
   //   "@" with " AT "
   public String replaceAt(String phrase)
   {
      String result = "";
      int pos = 0;
      int atpos = phrase.indexOf("@");
      while (atpos >= 0)
      {
         result = result + phrase.substring(pos, atpos) + " AT ";
         pos = atpos + 1;
         atpos = phrase.indexOf("@", pos);
      }
      result += phrase.substring(pos);
      
      return result;
   }

   public String replaceAt2(String phrase)
   {
      ArrayList<String> parts = new ArrayList<String>();
      for (int j=0; j<phrase.length(); j++)
      {
         String temp = phrase.substring(j,j+1);
         if (temp.equals("@"))
            parts.add(" AT ");
         else
            parts.add(temp);
      }
      
      String result = "";      
      for (int k=0; k<parts.size(); k++)
      {
         result += parts.get(k);
      }
      return result;
   }
   
   public String replaceAt3(String phrase)
   {
      int pos = phrase.indexOf("@");
   
      while (pos >= 0)
      {
         if (pos == 0) // first character
         {
            phrase = " AT " + phrase.substring(pos+1);
         }
         else if (pos == phrase.length()-1) // last character
         {
            phrase =  phrase.substring(0,pos) + " AT ";  
         }
         else
         {
            phrase =  phrase.substring(0, pos) + " AT " + 
                      phrase.substring(pos+1);
         }
         pos = phrase.indexOf("@");  
      }
      return phrase;
   }





   public String replaceAt4(String phrase)
   {
      Scanner fromString = new Scanner(phrase);
      fromString.useDelimiter("@");
      String result = "";
      if (fromString.hasNext())   // first piece
         result = fromString.next(); 
         
      while (fromString.hasNext())  // get the rest
      {
         result += " AT " + fromString.next();
       }
      return result;
   }

   public String replaceAt5(String phrase)
   {
      return phrase.replace("@", " AT ");
   }
   

B.   
   public ArrayList<String> replaceAllAts(Scanner input)
   {
      ArrayList<String> result = new ArrayList();
      while (input.hasNext())
       {
         result.add(replaceAt(input.nextLine()));
      }
      return result;
   }


   public ArrayList<String> replaceAllAts2(Scanner input)
   {
      ArrayList<String> result = new ArrayList();
      while (input.hasNext())
       {
         result.add(input.nextLine());
      }
      for (String current : result)
      {
         current = replaceAt(current);         
      }
      return result;
   }

   public ArrayList<String> replaceAllAts3(Scanner input)
   {
      ArrayList<String> result = new ArrayList();
      input.useDelimiter("\n");
      while (input.hasNext())
       {
         result.add(replaceAt3(input.next()));   // gets one line
      }
      return result;
   }


6. Part A
A1.
    // Constructor
   public Skier(String name, int number)
   {
      myName = name;
      myNumber = number;
      myTime = -1;
   }

A2.   
   // returns name of skier
   public String getName()
   {
      return myName;
   }
   
   // returns race number of skier
   public int getNumber()
   {
      return myNumber;
   }
    
   // returns best race time of skier so far, or a negative number if the
   //       skier has not raced yet.
   public int getTime()
   {   
      return myTime;
   }
   
A3.
   // sets skiers best time to raceTime if this is the first run
   // or if raceTime is faster than the skiers best time previously
   public void setTime(int raceTime)
   {
      if ((myTime < 0)|| (raceTime < myTime))
      {
         myTime = raceTime;
      }
   }
   
Part B
B1.
   // constructor - reads in skiers names and race numbers
   public SkiRace(Scanner input)
   {    mySkiers = new ArrayList<Skier>();
      while (input.hasNext())
      {
         mySkiers.add(new Skier(input.next(), input.nextInt()));
      }
   }

B2.
   // Print the name of the skier with the fastest time. If there
   // is a tie, then print all such names with that time.
   // Assume all times are between 0 and 1000
   public void PrintNamesWithBestSkiTimes()
   {
      // compute min time > 0
      int minRaceTime = 1001;
      for (Skier current : mySkiers)
      {
          int   currentTime = current.getTime();
            if (currentTime < minRaceTime)
          {
             minRaceTime = currentTime;
          }
      }
      
      // Print names of those with minimum race time
      for (Skier current: mySkiers)
      {
         if (current.getTime() == minRaceTime)
            System.out.println(current.getName());
      }
   }

   public void PrintNamesWithBestSkiTimes2()
   {
      // compute min time > 0
      int minRaceTime = mySkiers.get(0).getTime();
      String result = "";
      for (Skier current : mySkiers)
      {
          int   currentTime = current.getTime();
            if (currentTime < minRaceTime)
          {
             minRaceTime = currentTime;         // new fast time
             result = current.getName();        // get first name
          }
            else if (currentTime == minRaceTime)
            {
               result += " " + current.getName(); // another with same time
            }
      }
            System.out.println(result);
      
   }