This is an assignment for the course of Artificial Intelligence at the University of Macedonia .The goal of the assignment is to make a solver for any blocks configuration .

1. breadth (Breadth-First Search
2. depth (Depth-First Search)

1. best (Best-First Search))
2. astar (A-Star Search)

   Heuristics used:

   1. Heuristic 1 - this heuristic calculates the number of blocks that are currently not in the correct 'position'.

   2. Heuristic 2 - this heuristic is twice the number of blocks that must be moved once plus four times the number of blocks that must be moved twice. A block that must be moved once is a block that is currently on a block different to the block upon which it rests in the goal state or a block that has such a block somewhere below it in the same pile. A block that must be moved twice is a block that is currently on the block upon which it must be placed in the goal state, but that block is a block that must be moved or if there exists a block that must be moved twice somewhere below it (in the same pile).

   3. Heuristic 3 - this heuristic is similar to Heuristic 1. It calculates the difference between the current state and the goal state, but looks at the details of each block. If Block A in the goal state is supposed to be on top of Block B and under Block C and in the current state it is neither on top of B nor under C, then we add 2 to the heuristic and if it is either on top of B or under C we add 1.

python bw.py <method> <problem file> <solution file>

Problem files are in directory input_files you can choose from those problems or download more. Moreover you can choose your solution file name or use a standard name like 'solution.txt'.

cost_of_path: the number of moves taken to reach the goal

nodes_expanded: the number of nodes that have been expanded

max_search_depth:  the maximum depth of the search tree in the lifetime of the algorithm

running_time: the total running time of the search instance, reported in seconds

valid_solution: true or false depending on the check of solution.

The sequence of moves taken to reach the goal is written in solution file that user have typed above.

python bw.py astar probBLOCKS-6-1.pddl solution.txt 

SUCCESS
cost_of_path: 5
nodes_expanded: 16
max_search_depth: 5
running_time: 0.0020017623901367188
valid_solution: true

sequence of moves in solution.txt :

1. Move(A,F,D)
2. Move(B,table,A)
3. Move(C,table,B)
4. Move(F,table,C)
5. Move(E,table,F)

For more information regarding this project please check my comments inside the code .