dijkstra算法java实现

单源点最短路径Dijkstra算法的JAVA实现
关键字: dijkstra
package sinboy.datastructure;

import java.util.ArrayList;

public class Dijkstra ...{
    static ArrayList<Side> map = null;

    static ArrayList<Integer> redAgg = null;

    static ArrayList<Integer> blueAgg = null;

    static Side[] parents = null;

    public static void main(String[] args) ...{
        // 初始化顶点集
        int[] nodes = ...{ 0, 1, 3, 2, 4, 5,6 };

        // 初始化有向权重图
        map = new ArrayList<Side>();
        map.add(new Side(0, 1, 10));
        map.add(new Side(0, 3, 30));
        map.add(new Side(0, 4, 100));
        map.add(new Side(1, 2, 50));
        map.add(new Side(2, 4, 10));
        map.add(new Side(3, 2, 20));
        map.add(new Side(3, 4, 60));
        map.add(new Side(4, 5, 50));
        map.add(new Side(3, 5, 60));
        map.add(new Side(5, 6, 10));
        map.add(new Side(3, 6, 80));

        // 初始化已知最短路径的顶点集，即红点集，只加入顶点0
        redAgg = new ArrayList<Integer>();
        redAgg.add(nodes[0]);

        // 初始化未知最短路径的顶点集,即蓝点集
        blueAgg = new ArrayList<Integer>();
        for (int i = 1; i < nodes.length; i++)
            blueAgg.add(nodes[i]);

        // 初始化每个顶点在最短路径中的父结点,及它们之间的权重,权重-1表示无连通
        parents = new Side[nodes.length];
        parents[0] = new Side(-1, nodes[0], 0);
        for (int i = 0; i < blueAgg.size(); i++) ...{
            int n = blueAgg.get(i);
            parents[i + 1] = new Side(nodes[0], n, getWeight(nodes[0], n));
        }

        // 找从蓝点集中找出权重最小的那个顶点,并把它加入到红点集中
        while (blueAgg.size() > 0) ...{
            MinShortPath msp = getMinSideNode();
            if(msp.getWeight()==-1)
                msp.outputPath(nodes[0]);
            else
                msp.outputPath();
           
            int node = msp.getLastNode();
            redAgg.add(node);
            // 如果因为加入了新的顶点,而导致蓝点集中的顶点的最短路径减小,则要重要设置
            setWeight(node);
        }

    }

    /** *//**
     * 得到一个节点的父节点
     *
     * @param parents
     * @param node
     * @return
     */
    public static int getParent(Side[] parents, int node) ...{
        if (parents != null) ...{
            for (Side nd : parents) ...{
                if (nd.getNode() == node) ...{
                    return nd.getPreNode();
                }
            }
        }
        return -1;
    }

    /** *//**
     * 重新设置蓝点集中剩余节点的最短路径长度
     *
     * @param preNode
     * @param map
     * @param blueAgg
     */
    public static void setWeight(int preNode) ...{
        if (map != null && parents != null && blueAgg != null) ...{
            for (int node : blueAgg) ...{
                MinShortPath msp=getMinPath(node);
                int w1 = msp.getWeight();
                if (w1 == -1)
                    continue;
                for (Side n : parents) ...{
                    if (n.getNode() == node) ...{
                        if (n.getWeight() == -1 || n.getWeight() > w1) ...{
                            n.setWeight(w1);
                            n.setPreNode(preNode);//重新设置顶点的父顶点
                            break;
                        }
                    }
                }
            }
        }
    }

    /** *//**
     * 得到两点节点之间的权重
     *
     * @param map
     * @param preNode
     * @param node
     * @return
     */
    public static int getWeight(int preNode, int node) ...{
        if (map != null) ...{
            for (Side s : map) ...{
                if (s.getPreNode() == preNode && s.getNode() == node)
                    return s.getWeight();
            }
        }
        return -1;
    }

    /** *//**
     * 从蓝点集合中找出路径最小的那个节点
     *
     * @param map
     * @param blueAgg
     * @return
     */
    public static MinShortPath getMinSideNode() ...{
        MinShortPath minMsp = null;
        if (blueAgg.size() > 0) ...{
            int index = 0;
            for (int j = 0; j < blueAgg.size(); j++) ...{
                MinShortPath msp = getMinPath(blueAgg.get(j));
                if (minMsp == null || msp.getWeight()!=-1 &&  msp.getWeight() < minMsp.getWeight()) ...{
                    minMsp = msp;
                    index = j;
                }
            }
            blueAgg.remove(index);

        }
        return minMsp;
    }

    /** *//**
     * 得到某一节点的最短路径(实际上可能有多条,现在只考虑一条)
     * @param node
     * @return
     */
    public static MinShortPath getMinPath(int node) ...{
        MinShortPath msp = new MinShortPath(node);
        if (parents != null && redAgg != null) ...{
            for (int i = 0; i < redAgg.size(); i++) ...{
                MinShortPath tempMsp = new MinShortPath(node);
                int parent = redAgg.get(i);
                int curNode = node;
                while (parent > -1) ...{
                    int weight = getWeight(parent, curNode);
                    if (weight > -1) ...{
                        tempMsp.addNode(parent);
                        tempMsp.addWeight(weight);
                        curNode = parent;
                        parent = getParent(parents, parent);
                    } else
                        break;
                }

                if (msp.getWeight() == -1 || tempMsp.getWeight()!=-1 && msp.getWeight() > tempMsp.getWeight())
                    msp = tempMsp;
            }
        }

        return msp;
    }
}

/** *//**
* 图中的有向边，包括节点名及他的一个前向节点名，和它们之间的权重
*
*/
class Side ...{
    private int preNode; // 前向节点

    private int node;// 后向节点

    private int weight;// 权重

    public Side(int preNode, int node, int weight) ...{
        this.preNode = preNode;
        this.node = node;
        this.weight = weight;
    }

    public int getPreNode() ...{
        return preNode;
    }

    public void setPreNode(int preNode) ...{
        this.preNode = preNode;
    }

    public int getNode() ...{
        return node;
    }

    public void setNode(int node) ...{
        this.node = node;
    }

    public int getWeight() ...{
        return weight;
    }

    public void setWeight(int weight) ...{
        this.weight = weight;
    }

}

class MinShortPath ...{
    private ArrayList<Integer> nodeList;// 最短路径集

    private int weight;// 最短路径

    public MinShortPath(int node) ...{
        nodeList = new ArrayList<Integer>();
        nodeList.add(node);
        weight = -1;
    }

    public ArrayList<Integer> getNodeList() ...{
        return nodeList;
    }

    public void setNodeList(ArrayList<Integer> nodeList) ...{
        this.nodeList = nodeList;
    }

    public void addNode(int node) ...{
        if (nodeList == null)
            nodeList = new ArrayList<Integer>();
        nodeList.add(0, node);
    }

    public int getLastNode() ...{
        int size = nodeList.size();
        return nodeList.get(size - 1);

    }

    public int getWeight() ...{
        return weight;
    }

    public void setWeight(int weight) ...{
        this.weight = weight;
    }

    public void outputPath() ...{
        outputPath(-1);
    }

    public void outputPath(int srcNode) ...{
        String result = "[";
        if (srcNode != -1)
            nodeList.add(srcNode);
        for (int i = 0; i < nodeList.size(); i++) ...{
            result += "" + nodeList.get(i);
            if (i < nodeList.size() - 1)
                result += ",";
        }
        result += "]:" + weight;
        System.out.println(result);
    }

    public void addWeight(int w) ...{
        if (weight == -1)
            weight = w;
        else
            weight += w;
    }
}

运行结果如下：

[0,1]:10
[0,3]:30
[0,3,2]:50
[0,3,2,4]:60
[0,3,5]:90