Dijkstra算法

点对象

public class Vertex  implements Comparable<Vertex>{//必须实现此接口才能入栈
	private String name;//点的名字
	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getPath() {
		return path;
	}

	public void setPath(int path) {
		this.path = path;
	}

	public boolean isMarked() {
		return isMarked;
	}

	public void setMarked(boolean isMarked) {
		this.isMarked = isMarked;
	}

	public String getLast() {
		return last;
	}

	public void setLast(String last) {
		this.last = last;
	}

	private int path;//到该点的最短距离
	private boolean isMarked;//是否被标记
	private String last;//到该点的上一个点
	
	
	public Vertex(String name){
		this.name=name;
		this.path=Integer.MAX_VALUE;
		isMarked=false;
		this.last=null;		
	}
	
	 @Override
	    public int compareTo(Vertex o) {
	        return o.path > path?-1:1;
	    }
	
	

}

算法核心

import java.util.ArrayList;
import java.util.List;
import java.util.PriorityQueue;
import java.util.Queue;

public class Grap {
	
	private List<Vertex> vertexs;//所有的点
	private Queue<Vertex> queue;//没有访问过的点
	private int[][] edgs;//邻接矩阵
	
	public Grap(List<Vertex> v,int[][] edgs) {
		this.vertexs=v;
		this.edgs=edgs;
		initQueue();
	}
	
	//初始化队列
	public void initQueue(){
		queue=new PriorityQueue<>();
		for(Vertex v:vertexs){
			queue.add(v);
		}
	}
	
	
	//djkstra算法
	public void dijkstra(){
		while(!queue.isEmpty()){//当所有的都为true时结束
			Vertex v=queue.element();
			v.setMarked(true);
			//得到当前节点的邻接点
			List<Vertex> neighbors=getNeighbors(v);
			//更新邻接点
			updateNeighbors(v, neighbors);
			//该节点出队列
			queue.poll();
			
		}
		
	}
	
	//得到一个点的邻接点
	public List<Vertex> getNeighbors(Vertex v){
		List<Vertex> neighbors=new ArrayList<Vertex>();
		int position=vertexs.indexOf(v);
		for(Vertex neighbor:vertexs){
			int i=vertexs.indexOf(neighbor);
			if(i==position){
				continue;
			}
			
			if(edgs[position][i]!=Integer.MAX_VALUE&&neighbor.isMarked()){
				neighbors.add(neighbor);
			}
			
		}
		
		return neighbors;
		
	}
	
	//更新邻接点的值
	public void updateNeighbors(Vertex v,List<Vertex> neighbors){
		int position=vertexs.indexOf(v);
		for(Vertex neighbor:neighbors){
			int i=vertexs.indexOf(neighbor);
			int path=v.getPath()+edgs[position][i];
			if(path<neighbor.getPath()){
				vertexs.get(i).setPath(path);
				vertexs.get(i).setLast(v.getName());
			}			
		}
	}
	
	//输出
	public void  printPath(Vertex v) {		
		if(v.getLast()!=null){
			Vertex last;
			for(Vertex temp:vertexs){
				if(temp.getName()==v.getLast()){
					last=temp;
					printPath(last);
					System.out.print(" to ");
				}
			}
		}
		System.out.print(v.getName());
		
	}


}

测试

import java.util.ArrayList;
import java.util.List;

public class Main {

	public static void main(String[] args) {
		 List<Vertex> vertexs = new ArrayList<Vertex>();
	        Vertex a = new Vertex("v1");
	        a.setPath(0);
	        Vertex b = new Vertex("v2");
	        Vertex c = new Vertex("v3");
	        Vertex d = new Vertex("v4");
	        Vertex e = new Vertex("v5");
	        Vertex f = new Vertex("v6");
	        Vertex g =new Vertex("v7");
	        vertexs.add(a);
	        vertexs.add(b);
	        vertexs.add(c);
	        vertexs.add(d);
	        vertexs.add(e);
	        vertexs.add(f);
	        vertexs.add(g);
	        int[][] edges=new int[7][7];
	        for(int i=0;i<7;i++){
	        	for(int j=0;j<7;j++){
	        		edges[i][j]=Integer.MAX_VALUE;
	        	}
	        }
	        
	        edges[0][1]=2;
	        edges[0][3]=1;
	        edges[1][3]=3;
	        edges[1][4]=10;
	        edges[2][0]=4;
	        edges[2][5]=5;
	        edges[3][2]=2;
	        edges[3][4]=2;
	        edges[3][5]=8;
	        edges[3][6]=4;
	        edges[4][6]=6;
	        edges[6][5]=1;
	        Grap graph = new Grap(vertexs, edges);
	        graph.dijkstra();
	        System.out.print("v1 to ");
	        graph.printPath(g);
	       
	      

	}

}