Maze solver looping issue java

Question

So basically what I'm trying to do is creating a maze solving algorithm with the left hand rule but I'm encountering an issue that I can't seem to get passed.

The first two codes are the ones I'm working with and the problem I'm having is that when I try to loop the if-statements it just continues to draw a straight line up instead of turning left (in this case) and THEN looping back to the beginning and drawing a line until it hits a wall again. Note that I'm aware that this aint the finished product, I just want to make sure that alteast the first left turn and the loop works correctly.

import se.lth.cs.ptdc.window.SimpleWindow;
import se.lth.cs.ptdc.maze.*;

public class MazeTurtle extends Turtle {
protected int Maze;

public MazeTurtle(SimpleWindow w, int x, int y) {
    super(w, x, y);
}

public void walk(Maze maze) {
    Maze m = new Maze(1);
    Turtle t = new Turtle(w, m.getXEntry(), m.getYEntry());
    t.penDown();


    while(true){
        if(m.wallAtLeft(getDirection(), getX(), getY())){
            t.forward(1);
        }

        if(m.wallAtLeft(getDirection(), getX(), getY())){

            t.left(90);
        }


            /** The "wallInFront" could be ignored for now */
        if(m.wallInFront(getDirection(), getX(), getY())) {

            t.left(-90);
        }
        if(m.wallInFront(getDirection(), getX(), getY())){
            t.forward(1);
        }

         SimpleWindow.delay(10);
    }
}
}

Here is the the "Test" which tries to solve the maze with the given algorithm:

import se.lth.cs.ptdc.window.SimpleWindow;
import se.lth.cs.ptdc.maze.*;

public class MazeTest {

public static void main(String args[]) {

    Maze m = new Maze(1);
    SimpleWindow w = new SimpleWindow(600, 600, "MazeTest");
    MazeTurtle t = new MazeTurtle(w, m.getXEntry(), m.getYEntry());
    t.penDown();
    m.draw(w);
    t.walk(m);
}

}

Here is the maze class which i'm reffering to: http://pastebin.com/gxSeEc2U

And the turtle class that I'm using: http://pastebin.com/0RqbVudn

Answer 1

I'm pretty sure this should work out now

while ((m.atExit(x1, y1)) == false) {
        if (m.wallAtLeft(dir, x1, y1) == true) {
            t.forward(1);
            SimpleWindow.delay(10);
        }

        else if (m.wallAtLeft(dir, x1, y1) == false) {
            t.left(90);
            t.forward(1);
            SimpleWindow.delay(10);
        }

        if (m.wallInFront(dir, x1, y1) == true) {
            t.left(-90);
            t.forward(1);
        }

Answer 2

Try the following. This should check if there is a wall on the left, and go forward 1 if there is. If there is no wall on the left, it will turn left 90 degrees and move forward 1.

if(m.wallAtLeft(getDirection(), getX(), getY())){
    t.forward(1);
} else {
    t.left(90);
    t.forward(1);
}

Answer 3

I'm fairly new to Java but I'd try something like this

for (int i=0; i<500; i++) {
        SimpleWindow.delay(10);

        if (m.wallInFront(getDirection(), getX(), getY()) == false) {
            t.forward(1);   
        }

        if (m.wallInFront(getDirection(), getX(), getY()) == true) {
            t.left(90);
        }
}

To not hit the wall

Answer 4

    while (true) {
        if (m.wallAtLeft(getDirection(), getX(), getY())) {
            if (m.wallInFront(getDirection(), getX(), getY())) {
                t.left(-90);
            } else {
                t.forward(1);
                SimpleWindow.delay(10);
            }
        } else {
            t.left(90);
            t.forward(1);
            SimpleWindow.delay(10);
        }
    }

Answer 5

You are confused because the "wall at left" gives the answer relative to where the turtle is facing.

With your current algorithm....

• If there is a wall at the left, you will walk forward.
• Then, if there is a wall at left, turn 90 degrees to the left.
• (At this point you will face the wall.)
• Then, because there is a wall in front of you, you will turn right 90 degrees.
• Then you will walk forward if there is a wall in front of you.
• Repeat forever.

Any time you turn left because there is a wall to your left, you will immediately turn right because now the wall is in front of you.