求助！！

#include <iostream>
#include<queue>
#include <stack>
using namespace std;
#define int long long
int a[1001][1001],len,n,t,vis[1001][1001],m;
int dx[4]={1,-1,0,0};
int dy[4]={0,0,1,-1};
char record
[1001][1001],tmin[1001][1001];
const char c[5]={'D','U','R','L'};
struct node{
    int first,second,step;
};
bool in(int x,int y){
    return x>=1&&x<=n&&y>=1&&y<=m;
};
stack<char> st;
void prin(int x,int y){
    if(x==1&&y==1){
        return;
    }
    if(record[x][y]=='R'){
        prin(x,y-1);
    }
    if(record[x][y]=='L'){
        prin(x,y+1);
    }
    if(record[x][y]=='U'){
        prin(x+1,y);
    }
    if(record[x][y]=='D'){
        prin(x-1,y);
    }
    st.push(record[x][y]);
}
void pst(){
    for(int i=1;i<=2;i++){
        cout<<st.top();
        st.pop();
    }
}
void bfs(){
    queue<node> q;
    q.push({1,1,0});
    while(!q.empty()){
        auto now=q.front();q.pop();
        int x=now.first,y=now.second,step=now.step;
        if(x==n&&y==m){
            cout<< step<<endl;
            prin(n,m);
            pst();
            return;
        }
        for(int i=0;i<4;i++){
            int nx=x+dx[i],ny=y+dy[i];
            if(in(nx,ny)&&a[nx][ny]!=a[x][y]&&!vis[nx][ny]){
                vis[nx][ny]=true,record[nx][ny]=c[i],q.push({nx,ny,step+1});
            }
        }
    }
    cout<<-1;
}
signed main (){
       cin >> t;
while(t--){
    cin >> n >> m;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            vis[i][j]=0;
        }
    }
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            cin >>tmin[i][j];
            a[i][j]=tmin[i][j]-'0';
        }
    }
    bfs();
    }
    
}