AP Comp Sci 2015 FRQ Answers

ArraySums.java

public class ArraySums { //question 1
	public static int arraySum(int[] arr) { //part a
		int arraySum = 0;
		for (int i : arr)
			arraySum += i;
		return arraySum;
	}

	public static int[] rowSums(int[][] arr2D) { //part b
		int[] rowSums = new int[arr2D.length];
		for (int i = 0; i < arr2D.length; ++i)
			rowSums[i] = arraySum(arr2D[i]);
		return rowSums;
	}

	public static boolean isDiverse(int[][] arr2D) { //part c
		int[] rowSums = rowSums(arr2D);
		for (int rowSum : rowSums)
			for (int rowSum2 : rowSums)
				if (rowSum == rowSum2)
					return false;
		return true;
	}
}

HiddenWord.java

public class HiddenWord { //question 2
	private String word;

	public HiddenWord(String word) {
		this.word = word;
	}

	public String getHint(String guess) {
		String hint = "";
		for (int i = 0; i < word.length(); ++i)
			if (word.charAt(i) == guess.charAt(i))
				hint += word.charAt(i);
			else if (word.contains("" + guess.charAt(i)))
				hint += '+';
			else hint += '*';
		return hint;
	}
}

MultipleGroups.java

package numbergroup;

import java.util.Arrays;
import java.util.List;

public class MultipleGroups implements NumberGroup { //part c
	private List<NumberGroup> groupList;

	public MultipleGroups(NumberGroup... groups) {
		this.groupList = Arrays.asList(groups);
	}

	@Override
	public boolean contains(int i) {
		for (NumberGroup group : groupList)
			if (group.contains(i))
				return true;
		return false;
	}
}

NumberGroup.java

package numbergroup;

public interface NumberGroup { //part a
	boolean contains(int i);
}

Range.java

package numbergroup;

public class Range implements NumberGroup { //part b
	private int min;
	private int max;

	public Range(int min, int max) {
		this.min = min;
		this.max = max;
	}

	@Override
	public boolean contains(int i) {
		return this.min <= i && i <= this.max;
	}
}

SparseArray.java

package sparsearray;

import java.util.ArrayList;
import java.util.List;

public class SparseArray { //question 3
	private int numRows;
	private int numCols;

	private List<SparseArrayEntry> entries;

	public SparseArray() {
		entries = new ArrayList<>();
	}

	public int getNumRows() {
		return numRows;
	}

	public int getNumCols() {
		return numCols;
	}

	public int getValueAt(int row, int col) { //part a
		for (SparseArrayEntry entry : entries)
			if (entry.getRow() == row && entry.getCol() == col)
				return entry.getValue();
		return 0;
	}

	public void removeColumn(int col) { //part b
		for (int i = 0; i < entries.size(); ++i) {
			SparseArrayEntry entry = entries.get(i);
			if (entry.getCol() == col)
				entries.remove(entry);
			else if (entry.getCol() > col)
				entries.set(i, new SparseArrayEntry(entry.getRow(), entry.getCol() - 1, entry.getValue()));
		}
		--numCols;
	}
}

SparseArrayEntry.java

package sparsearray;

public class SparseArrayEntry { //question 3
	private int row;
	private int col;

	private int value;

	public SparseArrayEntry(int r, int c, int v) {
		row = r;
		col = c;
		value = v;
	}

	public int getRow() {
		return row;
	}

	public int getCol() {
		return col;
	}

	public int getValue() {
		return value;
	}
}