# Copyright 2010 Hakan Kjellerstrand hakank@gmail.com
#
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#
# Unless required by applicable law or agreed to in writing, software
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and

"""

n-queens problem in Google CP Solver.

N queens problem.

Faster than the previous versions:
- http://www.hakank.org/gogle_cp_solver/nqueens.py
- http://www.hakank.org/gogle_cp_solver/nqueens2.py

This model was created by Hakan Kjellerstrand (hakank@gmail.com)
"""
import sys, string
from constraint_solver import pywrapcp

def main(n=8, num_sol=0, print_sol=1):
# Create the solver.
solver = pywrapcp.Solver('n-queens')

#
# data
#
print "n:", n
print "num_sol:", num_sol
print "print_sol:", print_sol

# declare variables
q = [solver.IntVar(0,n-1, 'x%i' % i) for i in range(n)]

#
# constraints
#

# symmetry breaking

#
# search
#

db = solver.Phase(q,
solver.CHOOSE_MIN_SIZE_LOWEST_MAX,
solver.ASSIGN_CENTER_VALUE)

solver.NewSearch(db)
num_solutions = 0
while solver.NextSolution():
if print_sol:
qval = [q[i].Value() for i in range(n)]
print "q:", qval
for i in range(n):
for j in range(n):
if qval[i] == j:
print "Q",
else:
print "_",
print
print
num_solutions += 1
if num_sol > 0 and num_solutions >= num_sol:
break

solver.EndSearch()

print
print "num_solutions:", num_solutions
print "failures:", solver.Failures()
print "branches:", solver.Branches()
print "WallTime:", solver.WallTime(), "ms"

n = 8
num_sol = 0
print_sol = 1
if __name__ == '__main__':
if len(sys.argv) > 1:
n = int(sys.argv[1])
if len(sys.argv) > 2:
num_sol = int(sys.argv[2])
if len(sys.argv) > 3:
print_sol = int(sys.argv[3])

main(n, num_sol, print_sol)

# print_sol = False
# show_all = False
# for n in range(1000,1001):
#     print
#     main(n, num_sol, print_sol)