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2015 FRQ Week

• Study Plan
• This week, we were responsible for taking part in the 2015 AP Computer Science A Practice Exam.

Multiple Choice (Score: 30/39, but didn’t have time for last 5)

Question 22:

• 2D Arrays
• Why I got this wrong: My answer would 100% Error.

Question 26

• Topic: Writing Methods
• Why I got this wrong: This was some horrific code writen by CollegeBoard but I should have noticed that since the function is a static, the location of the value changes, but not the actual value

Question 27

• Topic: Arrays and Sorting
• Why I got it wrong: I noticed that this was a selection sort quite early, but forgot that the 1 and 6 would swap with each other, causing the mistake.

Question 31

• Topic: 2D Arrays
• Why I got it wrong: I actually was confused with the functionality of the code other than that of the front row

Didn’t have time for questions 35-39

FRQ (I was out of town and could only do 2 of them. Final Score: 25/36)

Question 1 (DiverseArray)

public class DiverseArray {
    public static int arraySum(int[] arr) {
        int count = 0;
        for (int i = 0; i < arr.length; i++) {
            count += arr[i];
        }
        return count;
    }

    public static int[] rowSums(int[][] arr2D) {
        int[] arr = new int[arr2D.length];
        int rowCount=0;
        for (int[] i : arr2D) {
            arr[rowCount] = arraySum(i);
            rowCount++;
        }
        return arr;
    }

    public static boolean isDiverse(int[][] arr2D) {
        int[] arr = rowSums(arr2D);
        for (int i = 0; i < arr.length; i++) {
            for (int j=i+1; j < arr.length; j++) {
                if (arr[i]==arr[j]) {
                    return false;
                }
            }

        }
        return true;
    }
}

Question 2 (HiddenWord):

public class HiddenWord {

    private String word;

    public HiddenWord(String guessedWord) {
        word = guessedWord;
    }

    public String getHint(String guess) {
        String preHint = "";

        for (int i = 0; i < guess.length(); i++) {
            if (guess.substring(i, i+1).equals(word.substring(i, i+1))) {
                preHint += guess.substring(i, i+1);
            }
            else if (word.indexOf(guess.substring(i, i+1)) != -1) {
                preHint += "+";
            }
            else {
                preHint += "*";
            }
        }
        return preHint;
    }
}

Question 4 (SparseArrayEntry):

public class SparseArrayEntry {

    public interface NumberGroup {
        boolean contains(int num);
    }

    public class Range implements NumberGroup {
        private int minValue;
        private int maxValue;

        public Range(int minValue, int maxValue) {
            this.minValue=minValue;
            this.maxValue=maxValue;
        }
        public boolean contains(int num) {
            return num >= minValue && num <= maxValue;
        }
    }
    
    public boolean contains(int num) {
         for (NumberGroup group : groupList) {
             if (group.contains(num)) {
                 return true;
             }
         }
         return false;
    }
}