# Copyright 2010 Hakan Kjellerstrand hakank@bonetmail.com
#
# Licensed under the Apache License, Version 2.0 (the "License"); 
# you may not use this file except in compliance with the License. 
# You may obtain a copy of the License at 
#
#     http://www.apache.org/licenses/LICENSE-2.0 
#
# Unless required by applicable law or agreed to in writing, software 
# distributed under the License is distributed on an "AS IS" BASIS, 
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
# See the License for the specific language governing permissions and 
# limitations under the License.

"""

  Knapsack problem in Google CP Solver.

  Simple knapsack problem.
  
  This model was created by Hakan Kjellerstrand (hakank@bonetmail.com)
  Also see my other Google CP Solver models: http://www.hakank.org/google_or_tools/
"""

from constraint_solver import pywrapcp

def knapsack(solver, values, weights, n):
    z = solver.IntVar(0, 10000)
    x = [solver.IntVar(0,1,"x(%i)"%i) for i in range(len(values))]
    solver.Add(z >= 0)
    solver.Add(z == solver.ScalProd(x, values))
    solver.Add(solver.ScalProd(x, weights) <= n)

    return [x, z]
 

def main(values, weights, n):
    # Create the solver.
    solver = pywrapcp.Solver('n-queens')

    #
    # data
    #
    print "values:", values
    print "weights:", weights
    print "n:", n
    print
    
    # declare variables
    

    #
    # constraints
    #
    [x, z] = knapsack(solver, values, weights, n)


    # objective
    objective = solver.Maximize(z,1)


    #
    # solution and search
    #
    solution = solver.Assignment()
    solution.Add(x)
    solution.Add(z)    


    # db: DecisionBuilder
    db = solver.Phase(x,
                 solver.CHOOSE_FIRST_UNBOUND,
                 solver.ASSIGN_MAX_VALUE)
    
    solver.NewSearch(db,[objective])
    num_solutions = 0
    while solver.NextSolution():  
        print "x:", [x[i].Value() for i in range(len(values))]
        print "z:", z.Value()
        print
        num_solutions += 1        
    solver.EndSearch()
    
    print
    print "num_solutions:", num_solutions
    print "failures:", solver.failures()
    print "branches:", solver.branches()
    print "wall_time:", solver.wall_time()


values =  [15, 100, 90, 60, 40, 15, 10,  1, 12, 12, 100]
weights = [ 2,  20, 20, 30, 40, 30, 60, 10, 21, 12,   2]
n = 102

if __name__ == '__main__':
    main( values, weights, n)