HDU1728

题解：

/*
bfs：
     WA了n次，主要是考虑策略时想法错了。
     其实每到一个点时就应该把改点以及该方向的点全都遍历一次，这样才能保证
     到达改点时是最优策略，其次，因为交叉关系，vis[][]应该放在while判断里面。
*/
import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;



public class Main {
    public static int row,column;
    public static int x2,y2;
    public static String[] map;
    public static boolean[][] mark;
    public static Queue<Block> queue;
    public static int[][] fx={{0,1},{1,0},{-1,0},{0,-1}};

    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int t=sc.nextInt();
        while(t-->0) {
            int x1,y1;
            row = sc.nextInt();
            column = sc.nextInt();
            map = new String[row];
            mark = new boolean[row][column];
            queue=new LinkedList<>();
            for (int i = 0; i < row; i++) {
                map[i]=sc.next();
            }
            int time=sc.nextInt();
            y1=sc.nextInt()-1;
            x1=sc.nextInt()-1;
            y2=sc.nextInt()-1;
            x2=sc.nextInt()-1;
            queue.offer(new Block(x1,y1,time+1));
            mark[x1][y1]=true;
            if(bfs()){
                System.out.println("yes");
            }else{
                System.out.println("no");
            }
        }

    }

    private static boolean bfs() {
        while(!queue.isEmpty()){
            Block b = queue.poll();
            if(b.i==x2&&b.j==y2){
                return true;
            }
            if(b.step==0){
                continue;
            }
            b.step--;
            for (int i = 0; i < 4; i++) {
                int xx=b.i+fx[i][0];
                int yy=b.j+fx[i][1];
                while(check(xx,yy)){
                    if(!mark[xx][yy]){
                        queue.offer(new Block(xx,yy,b.step));
                        mark[xx][yy]=true;
                    }
                    xx+=fx[i][0];
                    yy+=fx[i][1];
                }
            }
        }
        return false;
    }

    public static boolean check(int x,int y){
        if(x>=0&&x<row&&y>=0&&y<column&&map[x].charAt(y)!='*')
            return true;
        return false;
    }
    private static class Block{
        int i;
        int j;
        int step;

        public Block(int i, int j, int step) {
            this.i = i;
            this.j = j;
            this.step = step;
        }
    }


}