Free Response Solutions

Introduction

I created solutions to these as an exercise, trying to use methods I wasn't familiar with. Simpler solutions with methods inside of the AP CSA subset are located here.

These solutions may have issues; you can contact me with a description if you would like them fixed.

Questions

CollegeBoard® released the AP Computer Science A Free Response Questions on AP Central, accessible here.

Question 1 (DogWalker)

public int walkDogs(int hour) {
    int available = company.numAvailableDogs(hour);
    int dogsToWalk = Math.min(available, maxDogs);
    company.updateDogs(hour, dogsToWalk);
    return dogsToWalk;
}

public int dogWalkShift(int startHour, int endHour) {
    return java.util.stream.IntStream.rangeClosed(startHour, endHour)
            .map(h -> {
                int walked = walkDogs(h);
                int earnings = walked * 5;
                if (walked == maxDogs || (h >= 9 && h <= 17)) {
                    earnings += 3;
                }
                return earnings;
            })
            .sum();
}

Question 2 (SignedText)

public class SignedText {
    private final String first;
    private final String last;
    private final String signature;

    public SignedText(String firstName, String lastName) {
        this.first = firstName;
        this.last = lastName;
        this.signature = first.isEmpty() ? last : first.charAt(0) + "-" + last;
    }

    public String getSignature() {
        return signature;
    }

    public String addSignature(String text) {
        if (text.startsWith(signature)) {
            return text.substring(signature.length()) + signature;
        }
        if (text.endsWith(signature)) {
            return text;
        }
        return text + signature;
    }
}

Question 3 (Round.java)

public Round(String[] names) {
    competitorList = new ArrayList<>(names.length);
    java.util.stream.IntStream.range(0, names.length)
            .forEach(i -> competitorList.add(new Competitor(names[i], i + 1)));
}

public ArrayList<Match> buildMatches() {
    int size = competitorList.size();
    ArrayList<Match> matches = new ArrayList<>();
    java.util.stream.IntStream.range(0, size / 2)
            .forEach(k -> {
                int left = (size % 2 == 1) ? k + 1 : k;
                int right = size - 1 - k;
                if (left < right) {
                    matches.add(new Match(competitorList.get(left), competitorList.get(right)));
                }
            });
    return matches;
}

Question 4 (SumOrSameGame.java)

public SumOrSameGame(int numRows, int numCols) {
    java.util.Random rand = new java.util.Random();
    puzzle = new int[numRows][numCols];
    java.util.Arrays.setAll(puzzle, r -> {
        int[] row = new int[numCols];
        java.util.Arrays.setAll(row, c -> 1 + rand.nextInt(9));
        return row;
    });
}

public boolean clearPair(int row, int col) {
    int value = puzzle[row][col];
    if (value == 0) {
        return false;
    }
    for (int r = row; r < puzzle.length; r++) {
        for (int c = 0; c < puzzle[r].length; c++) {
            if (r == row && c == col) {
                continue;
            }
            int other = puzzle[r][c];
            if (other != 0 && (other == value || other + value == 10)) {
                puzzle[row][col] = 0;
                puzzle[r][c] = 0;
                return true;
            }
        }
    }
    return false;
}