CS3243_P2_Sudoku_f2.py

# CS3243 Introduction to Artificial Intelligence
# Project 2, Part 1: Sudoku

import sys
import copy
from collections import deque
from time import time

# Running script: given code can be run with the command:
# python file.py, ./path/to/init_state.txt ./output/output.txt

class Sudoku(object):
    def __init__(self, puzzle):
        # you may add more attributes if you need
        self.puzzle = puzzle # self.puzzle is a list of lists
        self.ans = copy.deepcopy(puzzle) # self.ans is a list of lists
        self.csp = CSP(puzzle)

    def solve(self):
        self.AC3(self.csp)
        assignment = self.backtrackingSearch(self.csp)
        for var in assignment:
            (i, j) = var.coordinate
            self.ans[i][j] = assignment[var]
        # self.ans is a list of lists
        return self.ans

    def backtrackingSearch(self, csp):
        assignment = csp.inferAssignment()
        return self.backtrack(csp, assignment)
    
    def backtrack(self, csp, assignment = dict()):
        if self.complete(assignment,csp):
            return assignment
        
        var = self.mrv(csp, assignment)
        for value in csp.currDomains[var].copy():
            if self.isConsistent(var, value, assignment, csp):
                assignment[var] = value
                #print(var)
                csp.unassignedVars.remove(var)
                removals = self.assume(var, value, csp)

                # self.printAssignment(assignment)
                # inferences = self.inference(csp, var, value)
                if self.forwardChecking(var, value, assignment, removals,csp):
                    result = self.backtrack(csp, assignment)
                    if result:
                        return result
                csp.unassignedVars.add(var)
                self.addBack(removals,csp)
        if var in assignment:
            del assignment[var]
        # del inferences from assignment
        return False

    def forwardChecking(self, var, val, assignment, removals, csp):
        # csp.copyCurrDomain()
        for N in csp.neighbour[var]:
            if N not in assignment:
                for value in csp.currDomains[N].copy():
                    if csp.constraints[(var,N)](val,value):
                        csp.currDomains[N].remove(value)
                        removals.append((N,value))
                if not csp.currDomains[N]:
                    return False    
        return True

    def assume(self, var, value, csp):
        # csp.copyCurrDomain()
        removals = list()
        for val in csp.currDomains[var]:
            if val != value:
                removals.append((var,val))
        csp.currDomains[var] = {value}
        return removals

    def addBack(self, removals, csp):
        for (var,val) in removals:
            csp.currDomains[var].add(val)

    def complete(self, assignment,csp):
        return len(assignment) == len(csp.variables)
    
    def isConsistent(self,var, val, assignment, csp):
        for key in assignment:
            if (var,key) in csp.constraints:
                if csp.constraints[(var,key)](val,assignment[key]):
                    return False
        return True
    
    def mrv(self,csp,assignment): # minimum remaining values
        # seq = csp.unassignedVars.copy() #filter(lambda var: var not in assignment,csp.variables)
        return min(csp.unassignedVars.copy(),key=lambda var: len(csp.currDomains[var]))

    def AC3(self,csp):
        arcs = set()
        for cons in csp.constraints:
            arcs.add(cons)
        csp.copyCurrDomain()
        while arcs:
            (xi, xj) = arcs.pop()
            if self.revise(csp, xi, xj):
                if not csp.currDomains[xi]:
                    return False
                # for xk in csp.neighbour[xi]:
                #     if xk != xj:
                arcs |= {(xk, xi) for xk in csp.neighbour[xi] if xk != xj and (xk, xi not in arcs)}
        return True
    def revise(self, csp, xi, xj):
        length = len(csp.currDomains[xi])
        if len(csp.currDomains[xj]) == 1:
            csp.currDomains[xi]-=csp.currDomains[xj]
            if len(csp.currDomains[xi])< length:
                return True
        return False
        # revised = False
        # print("before xi:",csp.currDomains[xi])
        # print("before xj:",csp.currDomains[xj])
        # for x in csp.currDomains[xi].copy():
        #     conflict = True
        #     #if any(map(lambda y : csp.constraints[(xi, xj)](x, y),csp.currDomains[xj])):
        #         #xi.domain.remove(x)
        #     for y in csp.currDomains[xj]:
        #         if not csp.constraints[(xi,xj)](x,y):
        #             conflict = False
        #         if not conflict:
        #             break
        #     if conflict:
        #         csp.currDomains[xi].remove(x)
        #         revised = True
        # if revised:        
        #     print("after",csp.currDomains[xi])
        #     print("------------------------")
        # return revised

    # you may add more classes/functions if you think is useful
    # However, ensure all the classes/functions are in this file ONLY
    # Note that our evaluation scripts only call the solve method.
    # Any other methods that you write should be used within the solve() method.
class Variable(object):
    def __init__(self, coordinate, value):
        self.coordinate = coordinate    # (x, y)
        self.value = value

    def __hash__(self):
        return hash(self.coordinate)

    def __eq__(self, var):
        return self.coordinate == var.coordinate

    def __str__(self):
        return str(self.coordinate)

    def isSameUnit(self, var):
        return self.isSameRow(var) or self.isSameCol(var) or self.isSameSquare(var) 

    def isSameRow(self, var):
        return self.coordinate[0] == var.coordinate[0]

    def isSameCol(self, var):
        return self.coordinate[1] == var.coordinate[1]

    def isSameSquare(self, var):
        ''' square refers to 3*3 square '''
        return (self.coordinate[0]//3, self.coordinate[1]//3) == (var.coordinate[0]//3, var.coordinate[1]//3)

class CSP(object):
    def __init__(self, puzzle): #removed constraints

        self.variables = set()  # set of var
        self.domains = dict()   # key = var, value = var_domain (set)
        self.neighbour = dict() # key = var, value = var_neighbour (set)

        # set of binary constraints (constraint function involving two var) represented by pair(scope, relation)
        # scope = (x, y), relation = f(x, y), where x, y are vars
        self.constraints = dict()
        self.initialiseCSP(puzzle)
        self.unassignedVars = self.variables.copy()
        self.currDomains = None

    def initialiseCSP(self,puzzle): #initialise csp
        # going through 2d list
        # for i in range(9):
        #     for j in range(9):
        self.variables = set((Variable((i, j), puzzle[i][j]) for i in range(9) for j in range(9)))
        # going through var set
        for var1 in self.variables:
            self.domains[var1] = set([1, 2, 3, 4, 5, 6, 7, 8, 9]) if not var1.value else set([var1.value])
            self.neighbour[var1] = set()
            for var2 in self.variables:
                if var1 != var2 and var1.isSameUnit(var2):
                    self.constraints[(var1, var2)] = lambda x,y: x==y #to check if in conflict
                    self.neighbour[var1].add(var2)
        
    def copyCurrDomain(self):
        ''' Create a copy of domains as currDomains '''
        if self.currDomains is None:
            self.currDomains = {var : set(self.domains[var]) for var in self.variables}
            # for var in self.variables:
            #     self.currDomains[var] = {i for i in self.domains[var]}
            
    def inferAssignment(self):
        assignment = {}
        #print("infer assignment")
        #self.copyCurrDomain()
        for var in self.currDomains:
            if len(self.currDomains[var])==1:
                assignment[var] = list(self.currDomains[var])[0]
                self.unassignedVars.remove(var)
        return assignment

if __name__ == "__main__":
    # STRICTLY do NOT modify the code in the main function here
    if len(sys.argv) != 3:
        print ("\nUsage: python CS3243_P2_Sudoku_XX.py input.txt output.txt\n")
        raise ValueError("Wrong number of arguments!")

    try:
        f = open(sys.argv[1], 'r')
    except IOError:
        print ("\nUsage: python CS3243_P2_Sudoku_XX.py input.txt output.txt\n")
        raise IOError("Input file not found!")

    puzzle = [[0 for i in range(9)] for j in range(9)]
    lines = f.readlines()

    i, j = 0, 0
    for line in lines:
        for number in line:
            if '0' <= number <= '9':
                puzzle[i][j] = int(number)
                j += 1
                if j == 9:
                    i += 1
                    j = 0

    sudoku = Sudoku(puzzle)
    start = time()
    ans = sudoku.solve()
    end = time()
    # outfile.close()
    # print(ans)
    with open(sys.argv[2], 'a') as f:
        for i in range(9):
            for j in range(9):
                f.write(str(ans[i][j]) + " ")
            f.write("\n")