CTCI 9.2

Imagine a robot sitting on the upper left corner of an X by Y grid. The robot can only move in two directions: right and down. How many 
possible paths are there for the robot to go from (0, 0) to (X, Y)?
FOLLOW UP
Imagine certain spots are "off limits", such that the robot cannot step on them. Design an algotithm to find a path for the robot from the 
top left to the bottom right.

CTCI 9.2.java

public static ArrayList<Point> findPath(){
    ArrayList<Point> path = new ArrayList<>();
    HashSet<Point> deadPoints = new HashSet<>();
    if(findPath(0, 0, path, deadPoints)) return path;
    else return null;
}

public static boolean findPath(int x, int y, ArrayList<Point> path, HashSet<Point> deadPoints){
    Point point = new Point(x, y);
    if(point.x == ENDX && point.y == ENDY){
        path.add(point);
        return true;
    }
    if(deadPoints.contains(point)) return false;
    path.add(point);
    if(point.x < ENDX){
        boolean rightProbe = findPath(point.x + 1, point.y, path, deadPoints);
        if(rightProbe) return true;
    }
    if(point.y < ENDY){
        boolean downProbe = findPath(point.x, point.y + 1, path, deadPoints);
        if(downProbe) return true;
    }
    path.remove(point);
    deadPoints.add(point);
    return false;
}