Tsp.java

/**
 * Copyright (c) 2011, Regents of the University of California
 * All rights reserved.
 * <p/>
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * <p/>
 * 1. Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 * <p/>
 * 2. Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following
 * disclaimer in the documentation and/or other materials provided
 * with the distribution.
 * <p/>
 * 3. Neither the name of the University of California, Berkeley nor
 * the names of its contributors may be used to endorse or promote
 * products derived from this software without specific prior written
 * permission.
 * <p/>
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
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 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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 */

package tests;

import janala.Main;

/**
 * @author Sudeep Juvekar <sjuvekar@cs.berkeley.edu>
 * @author Jacob Burnim <jburnim@cs.berkeley.edu>
 */
public class Tsp {

    private static class TspSolver {
        private final int N;
        private int D[][];
        private boolean visited[];
        private int best;

        public int nCalls;

        public TspSolver(int N, int D[][]) {
            this.N = N;
            this.D = D;
            this.visited = new boolean[N];
            this.nCalls = 0;
        }

        public int solve() {
            best = Integer.MAX_VALUE;

            for (int i = 0; i < N; i++)
                visited[i] = false;

            visited[0] = true;
            search(0, 0, N-1);

            return best;
        }

        private int bound(int src, int length, int nLeft) {
            return length;
        }

        private void search(int src, int length, int nLeft) {
            nCalls++;

            if (nLeft == 0) {
                if (length + D[src][0] < best)
                    best = length + D[src][0];
                return;
            }

            if (bound(src, length, nLeft) >= best)
                return;

            for (int i = 0; i < N; i++) {
                if (visited[i]) continue;

                visited[i] = true;
                search(i, length + D[src][i], nLeft - 1);
                visited[i] = false;
            }
        }
    }

    public static void main(String args[]) {
        final int N = 4;

        int D[][] = new int[N][N];

        for (int i = 0; i < N; i++) {
            for (int j = 0; j < N; j++) {
                int x = Main.readInt(0);
                Main.MakeSymbolic(x);
                Main.assume(x<10000?1:0);
                Main.assume(x>-10000?1:0);
                D[i][j] = x;
            }
        }

        TspSolver tspSolver = new TspSolver(N, D);

        // We only measure the complexity (i.e. path length) of the
        // Tsp solving.  That is, we count branches only from this
        // point forward in the execution.

        tspSolver.solve();
    }
}