You will implement a state-space search that will find a solution to the sixteenpuzzle. For this program, in addition to the state-space search control, you will need to implement at least two other classes.
One class will be a Queue class. This is not a difficult class to implement if you make use of the LinkedList collection class. For example, the add() method appends the parameter to the end of the list, and the remove() method removes and returns the object at the head of the list: hence you have a queue. There is also a size() method in the class, which makes it easy to implement
an is Empty() method for the Queue class.
The second class will be a State class. As in the example, a state should consist of a one dimensional, 16 location, integer array and another integer variable that holds the index of the space. In addition, since we want to print out the moves that solve the problem, we need something to hold the moves thus far. A String will work quite well, since the moves can be represented by the letters "U", "D", "L", "R". As a move is made, just concatenate the appropriate letter to the end of the String. And, to read the moves for a solution, the charAt() method in the String class can get to individual letters.