广度优先算法解决无向无权图的最短路径问题

package myalgorithm;
import java.util.LinkedList;
import java.util.Queue;
/*BFS用于记录的位置和值的结构*/
class node
{
    node(int cur,int valparam)
    {
        this.cur = cur;
        this.value = valparam;
    }
    int cur,value;
}
public class ShortPath {
    /*这里是对称点的，-1表示此路不通*/
    int[][] graph = {
            { 0,1,1,-1,-1},
            { 1,0,1, 1,-1},
            { 1,1,0, 1,1},
            {-1,1,1, 0,1},
            {-1,1,1,-1,0}
       
    };
    /*全局最短路径*/
    public int stepnum = 999;
    /*初始标记数组都为0*/
    public int[]mark = new int[graph.length];

  /*BFS算法*/
    public void BFS(node startPoint)
    {
        //起始点装入队列
        Queue<node> queue = new LinkedList<node>();
        queue.offer(startPoint);
        
        node t1;
        top:
        while(!queue.isEmpty())
        {
            //取队首，出队后不再入队，value也自此固定
            t1 = queue.poll();
            mark[t1.cur] = t1.value;//标记步数
            for(int i=0;i<5;i++)
            {
                //找到目的地5
                if(i==4 && graph[t1.cur][i] != -1)
                {
                    stepnum = t1.value + 1;//下一步可到
                    mark[t1.cur] = stepnum;
                    break top;
                }
                //继续接着找，把空路径添加到队列末尾
                //不是炸弹和围墙,并且没有被标记
                if(graph[t1.cur][i] != -1 
                        &&mark[i] == 0)
                {
                    //入队
                    queue.offer(new node(i,t1.value+1));
                }
            }
        }
    }
   
    /*main函数*/
    public static void main(String[] args) {
        ShortPath my = new ShortPath();
        long start = System.currentTimeMillis();
        my.BFS(new node(0,0));
        long end = System.currentTimeMillis();
        System.out.println("BFS step: " + my.stepnum + " time:" + (end-start));      
    }

}