TreasureHunt.java

import java.util.Random;

public class TreasureHunt {

    // ---------------------------
    // Inner class: Coordinate
    // ---------------------------

    public class Coordinate {
        private int x, y, z;
        private final boolean readonly;

        private Coordinate(int x, int y, int z) {
            this(x, y, z, false);
        }

        private Coordinate(int x, int y, int z, boolean readonly) {
            this.x = x;
            this.y = y;
            this.z = z;
            this.readonly = readonly;
        }

        public int x() { return x; }
        public int y() { return y; }
        public int z() { return z; }

        private void moveBy(int dx, int dy, int dz) {
            if (readonly)
                throw new UnsupportedOperationException("Cannot modify read-only coordinate");
            this.x += dx;
            this.y += dy;
            this.z += dz;
        }

        private void set(int x, int y, int z) {
            if (readonly)
                throw new UnsupportedOperationException("Cannot modify read-only coordinate");
            this.x = x;
            this.y = y;
            this.z = z;
        }

        public int manhattanTo(Coordinate other) {
            return Math.abs(this.x - other.x) + Math.abs(this.y - other.y) + Math.abs(this.z - other.z);
        }

        @Override
        public boolean equals(Object obj) {
            if (this == obj) return true;
            if (!(obj instanceof Coordinate)) return false;
            Coordinate o = (Coordinate) obj;
            return x == o.x && y == o.y && z == o.z;
        }

        @Override
        public String toString() {
            return "(" + x + "," + y + "," + z + ")";
        }
    }

    // ---------------------------
    // Inner Class: TrialResult
    // ---------------------------

    public class TrialResult {
        public final boolean foundGoal;
        public final int steps;

        private TrialResult(boolean foundGoal, int steps) {
            this.foundGoal = foundGoal;
            this.steps = steps;
        }
    }

    // ---------------------------
    // Inner Class: Collectible
    // ---------------------------

    public static class Collectible {
        private final boolean isHint;
        private final Object message;

        private Collectible() {
            this.isHint = false;
            this.message = (String) "goal";
        }

        private Collectible(int hintDist, int[] goalDistRange) {
            this.isHint = true;
            this.message = new Object[]{hintDist, goalDistRange};
        }

        private static Collectible goal() {
            return new Collectible();
        }

        private static Collectible hint(int distToPrev, int[] goalRange) {
            return new Collectible(distToPrev, goalRange);
        }

        public Object[] getMessage() {
            if (!isHint) return null;
            return (Object[]) this.message;
        }

        public boolean isHint() {
            return this.isHint;
        }
    }

    // ---------------------------
    // Fields
    // ---------------------------

    public final int edgeLength = 20;
    private final Collectible[][][] matrix;
    private final Coordinate[] hintCoords;
    private final Coordinate goalCoord;
    private final Coordinate currentCoord;
    private static final Random rand = new Random();
    private int steps = 0;

    // ---------------------------
    // Constructor
    // ---------------------------

    public TreasureHunt() {
        this.matrix = new Collectible[edgeLength][edgeLength][edgeLength];
        this.hintCoords = new Coordinate[9];
        this.currentCoord = new Coordinate(0, 0, 0);

        this.goalCoord = createRandomCoord(true);
        setHintCoords();
        populateMatrix();
    }

    // ---------------------------
    // Public API (for students)
    // ---------------------------

    public Coordinate position() {
        return currentCoord;
    }

    public void jumpTo(int x, int y, int z) throws IllegalArgumentException {
        if (x < 0 || x >= edgeLength)
            throw new IllegalArgumentException("Error: Cannot set x to " + x + ". Out of bounds");
        if (y < 0 || y >= edgeLength)
            throw new IllegalArgumentException("Error: Cannot set y to " + y + ". Out of bounds");
        if (z < 0 || z >= edgeLength)
            throw new IllegalArgumentException("Error: Cannot set z to " + z + ". Out of bounds");

        currentCoord.set(x, y, z);
        steps++;
    }

    public Collectible search() {
        return matrix[currentCoord.x()][currentCoord.y()][currentCoord.z()];
    }

    public TrialResult submit() {
        boolean found = currentCoord.equals(goalCoord);
        return new TrialResult(found, steps);
    }


    // ---------------------------
    // Internal logic
    // ---------------------------

    private int rand_in_range() {
        return rand.nextInt(this.edgeLength);
    }

    private Coordinate createRandomCoord(boolean readonly) {
        return new Coordinate(rand_in_range(), rand_in_range(), rand_in_range(), readonly);
    }

    private void setHintCoords() {
        int count = 0;
        while (count < 9) {
            Coordinate newCoord = createRandomCoord(true);
            boolean duplicate = false;
            for (int i = 0; i < count; i++) {
                if (hintCoords[i].equals(newCoord)) {
                    duplicate = true;
                    break;
                }
            }
            if (!duplicate && !newCoord.equals(goalCoord)) {
                hintCoords[count++] = newCoord;
            }
        }
    }

    private void populateMatrix() {
        populateMatrixGoal();
        populateMatrixHints();
    }

    private void populateMatrixGoal() {
        this.matrix[this.goalCoord.x()][this.goalCoord.y()][this.goalCoord.z()] = Collectible.goal();
    }

    private void populateMatrixHints() {
        final int RANGE_SIZE = 5;

        for (int i = 0; i < hintCoords.length; i++) {
            Coordinate current = hintCoords[i];
            Coordinate prev = hintCoords[(i - 1 + hintCoords.length) % hintCoords.length];

            int distToPrev = current.manhattanTo(prev);
            int distToGoal = current.manhattanTo(goalCoord);

            int halfSpan = rand.nextInt(RANGE_SIZE + 1);
            int low = Math.max(0, distToGoal - halfSpan);
            int high = Math.min(edgeLength * 3, distToGoal + (RANGE_SIZE - halfSpan));

            int[] rangeToGoal = new int[] { low, high };

            matrix[current.x()][current.y()][current.z()] = Collectible.hint(distToPrev, rangeToGoal);
        }
    }
}