/*
 * Copyright 2017 Darian Sastre darian.sastre@minimaxlabs.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.
 *
 * ************************************************************************
 *
 *  Coins grid problem in Google CP Solver.
 *
 *  Problem from
 *  Tony Hurlimann: "A coin puzzle - SVOR-contest 2007"
 *  http://www.svor.ch/competitions/competition2007/AsroContestSolution.pdf
 *  "
 *  In a quadratic grid (or a larger chessboard) with 31x31 cells, one should
 *  place coins in such a way that the following conditions are fulfilled:
 * 	  1. In each row exactly 14 coins must be placed.
 * 	  2. In each column exactly 14 coins must be placed.
 *    3. The sum of the quadratic horizontal distance from the main diagonal
 *    	 of all cells containing a coin must be as small as possible.
 *    4. In each cell at most one coin can be placed.
 *  The description says to place 14x31 = 434 coins on the chessboard each row
 *  containing 14 coins and each column also containing 14 coins.
 *  "
 *
 *  This is a Java MIP version of
 *  	  http://www.hakank.org/google_or_tools/coins_grid_mip.py
 *
 *  	  which is the MIP version of
 *  		http://www.hakank.org/google_or_tools/coins_grid.py
 *
 *  	  by Hakan Kjellerstrand (hakank@gmail.com).
 *
 *  Java version by Darian Sastre (darian.sastre@minimaxlabs.com)
 */
package com.google.ortools.contrib;

import com.google.ortools.linearsolver.*;

public class CoinsGridMIP {
  static {
    System.loadLibrary("jniortools");
  }

  private static MPSolver createSolver(String solverType) {
    return new MPSolver("MIPDiet", MPSolver.OptimizationProblemType.valueOf(solverType));
  }

  private static void solve(String solverType) {
    MPSolver solver = createSolver(solverType);

    /** invariants */
    int n = 31;
    int c = 14;

    /** variables */
    MPVariable[][] x = new MPVariable[n][n];
    for (int i = 0; i < n; i++) {
      x[i] = solver.makeBoolVarArray(n);
    }

    /** constraints & objective */
    MPConstraint[] constraints = new MPConstraint[2 * n];
    MPObjective obj = solver.objective();

    for (int i = 0; i < n; i++) {
      constraints[2 * i] = solver.makeConstraint(c, c);
      constraints[2 * i + 1] = solver.makeConstraint(c, c);

      for (int j = 0; j < n; j++) {
        constraints[2 * i].setCoefficient(x[i][j], 1);
        constraints[2 * i + 1].setCoefficient(x[j][i], 1);

        obj.setCoefficient(x[i][j], (i - j) * (j - i));
      }
    }

    solver.solve();

    for (int i = 0; i < n; i++) {
      for (int j = 0; j < n; j++) {
        System.out.print((int) x[i][j].solutionValue() + " ");
      }
      System.out.println();
    }
  }

  public static void main(String[] args) {
    try {
      System.out.println("---- Integer programming example with SCIP (recommended) ----");
      solve("SCIP_MIXED_INTEGER_PROGRAMMING");
    } catch (java.lang.IllegalArgumentException e) {
      System.err.println("Bad solver type: " + e);
    }
    try {
      System.out.println("---- Integer programming example with CBC ----");
      solve("CBC_MIXED_INTEGER_PROGRAMMING");
    } catch (java.lang.IllegalArgumentException e) {
      System.err.println("Bad solver type: " + e);
    }
    try {
      System.out.println("---- Integer programming example with GLPK ----");
      solve("GLPK_MIXED_INTEGER_PROGRAMMING");
    } catch (java.lang.IllegalArgumentException e) {
      System.err.println("Bad solver type: " + e);
    }
  }
}

@@ -2017,29 +2017,18 @@
 tic 
-MPSolver createS
+void s
 olve
-r
 (Str
@@ -2053,133 +2053,69 @@
     
-return new MPSolver(%22MIPDiet%22, MPSolver.OptimizationProblemType.valueOf(solverType));%0A  %7D%0A%0A  private static void solve(String
+System.out.println(%22---- Integer programming example with %22 +
  sol
@@ -2118,26 +2118,26 @@
  solverType)
- %7B
+;%0A
 %0A    MPSolve
@@ -2147,16 +2147,25 @@
 olver = 
+MPSolver.
 createSo
@@ -2169,27 +2169,75 @@
 eSolver(
-solverType)
+%22CoinsGridMIP%22, solverType);%0A    if (solver == null) return
 ;%0A%0A    /
@@ -3195,350 +3195,41 @@
     
-try %7B%0A      System.out.println(%22---- Integer programming example with SCIP (recommended) ----%22);%0A      solve(%22SCIP_MIXED_INTEGER_PROGRAMMING%22);%0A    %7D catch (java.lang.IllegalArgumentException e) %7B%0A      System.err.println(%22Bad solver type: %22 + e);%0A    %7D%0A    try %7B%0A      System.out.println(%22---- Integer programming example with CBC ----
+solve(%22SCIP%22);%0A    solve(%22CBC
 %22);%0A
-  
     
@@ -3239,240 +3239,16 @@
 ve(%22
-CBC_MIXED_INTEGER_PROGRAMMING%22);%0A    %7D catch (java.lang.IllegalArgumentException e) %7B%0A      System.err.println(%22Bad solver type: %22 + e);%0A    %7D%0A    try %7B%0A      System.out.println(%22---- Integer programming example with GLPK ----
+GLPK
 %22);%0A
-  
     
@@ -3258,151 +3258,14 @@
 ve(%22
-GLPK_MIXED_INTEGER_PROGRAMMING%22);%0A    %7D catch (java.lang.IllegalArgumentException e) %7B%0A      System.err.println(%22Bad solver type: %22 + e);%0A    %7D
+SAT%22);
 %0A  %7D

fix contrib example