SOLUTION TASK 3.01

public void act() {
    int count = 0;

    while (!treeFront()) {
        move();

        if (onLeaf()) {
            count = count + 1;
        }
    }

    System.out.println("The result is: " + count);
    
    stop();
}

SOLUTION TASK 3.02

public class MyKara extends Kara {
    
    boolean goingRight = true;
    
    public void act() {
        invertField();
        
        if (treeFront()) {
            if (goingRight) {
                // we are at the right border
                turnAroundRight();
            } else {
                // we are at the left border
                turnAroundLeft();
            }
        } else {
            move();
        }
    }
    
    public void turnAroundRight() {
        if (treeRight()) {
            // we are in the bottom right corner
            stop();
        } else {
            turnRight();
            move();
            turnRight();
            goingRight = false;
        }
    }
    
    public void turnAroundLeft() {
        if (treeLeft()) {
            // we are in the bottom left corner
            stop();
        } else {
            turnLeft();
            move();
            turnLeft();
            goingRight = true;
        }
    }

    public void invertField() {
        if (onLeaf()) {
            removeLeaf();
        } else {
            putLeaf();
        }
    }
}

SOLUTION TASK 3.03

public class MyKara extends Kara {
    
    boolean goingRight = true;
    int step = 0;
    
    public void act() {
        putLeafIfEvenStep();
        
        if (treeFront()) {
            if (goingRight) {
                // we are at the right border
                turnAroundRight();
            } else {
                // we are at the left border
                turnAroundLeft();
            }
        } else {
            move();
            step = step + 1;
        }
    }
    
    public void turnAroundRight() {
        if (treeRight()) {
            // we are in the bottom right corner
            stop();
        } else {
            turnRight();
            move();
            turnRight();
            goingRight = false;
            step = step + 1;
        }
    }
    
    public void turnAroundLeft() {
        if (treeLeft()) {
            // we are in the bottom left corner
            stop();
        } else {
            turnLeft();
            move();
            turnLeft();
            goingRight = true;
            step = step + 1;
        }
    }

    public void putLeafIfEvenStep() {
        if (step % 2 == 0) {
            // even step number --> put a leaf
            putLeaf();
        }
    }
}

SOLUTION TASK 3.04

public class MyKara extends Kara {
    int longestRow = 0;

    public void act() {
        while (!onLeaf()) {
            if (treeFront()) {
                countRow();
            } else {
                move();
            }
        }

        System.out.println("The longest tree line is " + longestRow + 
                " trees long");
        stop();
    }

    public void countRow() {
        int currentRow = 0;
        turnLeft();

        while (treeRight()) {
            currentRow = currentRow + 1;
            move();
        }

        // go around tree line
        turnRight();
        move();
        move();
        turnRight();

        // go back down
        int i = 0;
        while (i < currentRow) {
            move();
            i = i + 1;
        }

        turnLeft();

        // test whether the current row is longer
        if (currentRow > longestRow) {
            longestRow = currentRow;
        }
    }
}

SOLUTION TASK 3.05

See the solution scenario in the downloads section.