Move java examples

examples/java/CoinsGridMIP.java

@@ -0,0 +1,116 @@
+/*
+ * 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)
+ */
+
+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);
+		}
+	}
+}