题目：sdnu1220

#include<iostream>
#include<queue>
#include<algorithm>
#include<cstring>
using namespace std;
int n,m;
struct node
{
	int x;
	int y;
};
struct edge 
{
	int x;
	int y;
	int s=0;
	char step;
}rec[20][20];

char ditu[20][20];
int next[4][2]={1,0,0,-1,0,1,-1,0};
int book[20][20];

void bfs()
{
	queue<node>q;
	node begin;
	begin.x =0;
	begin.y =0;
	book[0][0]=1;
	q.push(begin);
	while(!q.empty())
	{
		node pre=q.front();
		q.pop();
		for(int i=0;i<=3;i++)
		{
			node now;
			now.x=pre.x+next[i][0];
			now.y=pre.y+next[i][1];
			if(now.x<0||now.y<0||now.x>n-1||now.x>m-1)
			continue;
			if(book[now.x][now.y]==0)
			{
				book[now.x][now.y]=1;
				rec[now.x][now.y].x=pre.x;
				rec[now.x][now.y].y=pre.y;
				rec[now.x][now.y].s=rec[pre.x][pre.y].s+1;
				if(i==0)
				rec[now.x][now.y].step='D';
				if(i==1)
				rec[now.x][now.y].step='L';
				if(i==2)
				rec[now.x][now.y].step='R';
				if(i==3)
				rec[now.x][now.y].step='U';
				q.push(now);
				
			}
		}
	
	}
}

void digui(int x,int y)
{
	if(x==0&&y==0)
	{
	
		return;
	}
	digui(rec[x][y].x,rec[x][y].y);
	cout<<rec[x][y].step;
}
int main()
{
	while(cin>>n>>m)
	{
	
	for(int i=0;i<n;i++)
	{
      for(int j=0;j<m;j++)
	   cin>>ditu[i][j];
	}
    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++)
        {
            if (ditu[i][j] == '0')book[i][j] = 0;
            else book[i][j] = 1;
        }	
     bfs(); 
     cout<<rec[n-1][m-1].s<<endl;
     digui(n-1,m-1);
     cout<<endl;
     memset(ditu,0,sizeof(ditu));
    }

	return 0;
}