旅行售貨員問題-分支界限法

旅行售貨員問題分支界限法

package test;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

/**
 * Created by saishangmingzhu on 2018/12/13.
 * 旅行售貨員問題
 */
public class TravellingSalesmanProblem {

    //圖
    private int[][] pointIndex=new int[][]{
            {0,30,6,4},
            {30,0,5,10},
            {6,5,0,20},
            {4,10,20,0}};
    public static void main(String[] arg){
        new TravellingSalesmanProblem().branchAndBoundMethod();
    }

    /**
     * 分支界限法-優先隊列式
     * 優先隊列式求解時，到達第一個沒有子結點的活結點時，即爲最優解
     */
    public void branchAndBoundMethod() {
        List<Point> pointList=new ArrayList<>();
        pointList.add(new Point(0,"1"));
        pointList.add(new Point(1,"2"));
        pointList.add(new Point(2,"3"));
        pointList.add(new Point(3,"4"));
        Node root=new Node();
        root.point=pointList.get(0);
        root.childPointList.addAll(pointList);
        root.childPointList.remove(root.point);

        Node minNode=new Node();
        minNode.value=Integer.MAX_VALUE;

        List<Node> currentLiveNodeList=new ArrayList<>();
        currentLiveNodeList.add(root);
        while (currentLiveNodeList.size()>0) {
            Node liveNode = currentLiveNodeList.get(0);
            List<Point> childPointList = liveNode.childPointList;
            for (Point childPoint : childPointList) {
                int value=pointIndex[childPoint.index][liveNode.point.index];
                if (value!=0) {
                    Node childNode = new Node();
                    childNode.parentNode=liveNode;
                    childNode.point = childPoint;
                    childNode.childPointList.addAll(childPointList);
                    childNode.childPointList.remove(childPoint);
                    childNode.value = liveNode.value + value;
                    if (childNode.childPointList.size() == 0 ) {
                        if (pointIndex[0][childPoint.index] != 0) {
                            childNode.value += pointIndex[0][childPoint.index];
                            if (childNode.value<minNode.value){
                                minNode.value=childNode.value;
                                minNode.point=childNode.point;
                                minNode.parentNode=childNode.parentNode;
                            }
                        } else {
                            continue;
                        }
                    }
                    currentLiveNodeList.add(childNode);
                }
            }
            currentLiveNodeList.remove(liveNode);
            Collections.sort(currentLiveNodeList, new Comparator<Node>() {
                @Override
                public int compare(Node o1, Node o2) {
                    return o2.value-o1.value;
                }
            });
        }

        System.out.println(minNode.value);
        getParents(minNode);
    }

    private void getParents(Node node){
        if (node==null){
            return;
        }
        getParents(node.parentNode);
        System.out.println(node.point.name);
    }

    class Node{
        private Node parentNode;
        private Point point;
        private List<Node> childNodeList=new ArrayList<>();
        private List<Point> childPointList=new ArrayList<>();
        private int value;
    }

    class Point{
        private int index;
        private String name;

        public Point(int index, String name) {
            this.index = index;
            this.name = name;
        }
    }
}