Chin-Kai Chang 
chinkaic@usc.edu
7557-0110-81
CSCI460 HW2 8-puzzle problem

Compile: javac Main.java

Usage: java Main input_file.txt output_file.txt

Main.java : Program entry point
Node.java : Puzzle Node struct
PriorityQueue.java : Simple priority queue
Puzzle.java : Puzzle board
Solver.java : Solving program
Xy.java : location class