APCS Written Test Practice 2015

APCS-Test-Practice-2015.java

// 1a
public static int arraySum(int[] arr) {
	int sum = 0;
	for(int elem : arr)
		if(elem != null)
			sum += elem;
	return sum;
}

// 1b
public static int[] rowSums(int[][] arr2D) {
	int[] out = new int[arr2D.length];
	for(int i = 0; i < out.length; i++)
		out[i] = arraySum(i);
	return out;
}

// 1c
public static boolean isDiverse(int[][] arr2D) {
	int[] arr1D = rowSums(arr2D);
	for(int i = 0; i < arr1D.length; i++)
		for(int j = 0; j < i; j++)
			if(arr1D[i] == arr1D[j])
				return false;
	return true;
}

// 2
public class HiddenWord {
	private String word;
	
	public HiddenWord(String newWord) {
		word = newWord;
	}
	
	pulic String getHint(String guess) {
		String toReturn = "";
		for(int i = 0; i < guess.length(); i++) {
			if(guess.charAt(i).equals(word.charAt(i)))
					// Answer keys uses substring(i, i + 1) instead of charAt(i).
					// Is charAt(i) fine?
				toReturn += guess.charAt(i);
			else if(word.indexOf(guess.charAt(i)) != -1)
				toReturn += "+";
			else
				toReturn += "*";
		}
		return toReturn;
	}
}

// 3a
public int getValueAt(int row, int col) {
	for(SparseArrayEntry elem : entries) {
		if(elem.getRow() == row && elem.getCol() == col)
			return elem.getValue();
	}
	return 0;
}

// 3b
public void removeColumn(int col) {
	for(int i = 0; i < entries.size(); i++) {
		if(entries.get(i).getCol() == col) {
			entries.remove(i);
			i--;
		} else if(entries.get(i).getCol() > col) {
			entries.set(i, new SparseArrayEntry(entries.get(i).getRow(), entries.get(i).getCol() - 1,
					entries.get(i).getValue()));
		}
	}
	numCols--;
}

// 4a
public interface NumberGroup {
	// I didn't know whether the interface should have an array of integers or not, but I guessed not.
	boolean contains(int num);
}

// 4b
// This is what I originally did; apparently it didn't want the class to actually have an array? It never specified...
//public class Range implements NumberGroup {
	int[] myArray;
	
	public Range(int low, int high) {
		myArray = new int[high - low + 1];
		int current = low;
		for(int i = 0; i < myArray.length; i++) {
			myArray[i] = current;
			current++;
		}
	}
}
public class Range implements NumberGroup {
	// I forgot private on these variables the first time
	private int min;
	private int max;
	
	public Range(int mi, int ma) {
		min = mi;
		max = ma;
	}
	
	public boolean contains(int num) {
		return (min <= num && num <= max);
	}
}

// 4c
public boolean contains(int num) {
	for(NumberGroup elem : groupList) {
		if(elem.contains(num)) return true;
	}
	return false;
}