Labyrinth code in Graph Algorithms does not work!!!! about dsa HOT 2 CLOSED

import java.io.*;
import java.util.*;
 
@SuppressWarnings("all")
public class Main {
    static int endi, endj;
 
    static void solve() throws IOException{
        StringTokenizer st;
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter output = new BufferedWriter(new OutputStreamWriter(System.out));
        st = new StringTokenizer(br.readLine());
        int n = Integer.parseInt(st.nextToken());
        int m = Integer.parseInt(st.nextToken());
        char mat[][] = new char[n][m];
        char dir[][] = new char[n][m]; 
        fill2D(dir, '#');
        int si = 0, sj = 0;
        for (int i = 0; i < n; i++) {
            st = new StringTokenizer(br.readLine());
            mat[i] = st.nextToken().toCharArray();
            for (int j = 0; j < m; j++) {
                if (mat[i][j] == 'A') {
                    si = i;
                    sj = j;
                } else if (mat[i][j] == 'B') {
                    endi = i;
                    endj = j;
                }
            }
            
        }
        
        boolean f = false;
        ArrayDeque<int[]> q = new ArrayDeque<>();
        q.offerLast(new int[]{si, sj});
        while (!q.isEmpty()) {
            int[] tmp = q.pollFirst();
            // System.out.println(tmp);
            if (tmp[0] == endi && tmp[1] == endj) {
                f = true;
                break;
            }
            
 
            int nx, ny;
            // Left
 
            nx = tmp[0];
            ny = tmp[1] - 1;
            if (!(nx < 0 || nx >= n || ny < 0 || ny >= m || mat[nx][ny] == '#')) {
                q.offerLast(new int[]{nx,ny});
                dir[nx][ny] = 'L';
                mat[nx][ny] = '#';
 
            }
 
            // Right
 
            nx = tmp[0];
            ny = tmp[1] + 1;
            if (!(nx < 0 || nx >= n || ny < 0 || ny >= m || mat[nx][ny] == '#')) {
                q.offerLast(new int[]{nx,ny});
                dir[nx][ny] = 'R';
                mat[nx][ny] = '#';
            }
 
            // Up
            nx = tmp[0] - 1;
            ny = tmp[1];
            if (!(nx < 0 || nx >= n || ny < 0 || ny >= m || mat[nx][ny] == '#')) {
                q.offerLast(new int[]{nx,ny});
                dir[nx][ny] = 'U';
                mat[nx][ny] = '#';
            }
            // Down
            nx = tmp[0] + 1;
            ny = tmp[1];
            if (!(nx < 0 || nx >= n || ny < 0 || ny >= m || mat[nx][ny] == '#')) {
                q.offerLast(new int[]{nx,ny});
                dir[nx][ny] = 'D';
                mat[nx][ny] = '#';
            }
            // System.out.println(q);
        }
        StringBuilder s = new StringBuilder();
        if (!f)
        System.out.println("NO");
        else {
            int nx = endi, ny = endj;
            while(nx!=si || ny!=sj)
            {
                s.append(dir[nx][ny]);
                switch(dir[nx][ny])
                {
                    case 'L':{ny++;break;}
                    case 'R':{ny--;break;}
                    case 'U':{nx++;break;}
                    case 'D':{nx--;break;}
                }
            }
            s.reverse();
            output.write("YES\n");
            output.write(s.length() + "\n");
            output.write(s.toString());
        }
        output.flush();
        // for (int i = 0; i < n; i++) {
        // for (int j = 0; j < m; j++) {
        // sc.print(dir[i][j]);
        // }
        // sc.println();
        // }
        /*
         * for(int i = 0;i<n;i++) { for(int j = 0; j<m;j++) { sc.print(mat[i][j]); }
         * sc.println(); }
         */
 
    }
 
    public static void main(String[] args) throws IOException{
        // FastReader(true) for File I/O
        // FastReader() for terminal I/O
        if (args.length > 0 && args[0].equals("local")) {
            //FastReader sc = new FastReader(true);
            // CODE BEGIN
            // for(int T = sc.nextInt();T > 0;T--)
            solve();
            // CODE END
            //sc.closer();
        } else {
            //FastReader sc = new FastReader();
            // CODE BEGIN
            // for(int T = sc.nextInt();T > 0;T--)
            solve();
            // CODE END
            //sc.closer();
 
        }
    }
 
    static int gcd(int a, int b) {
        if (b == 0)
            return a;
        else
            return gcd(b, a % b);
    }
 
    public static int lcm(int a, int b) {
        return (a / gcd(a, b)) * b;
    }
 
    static void sort(int[] a) {
        ArrayList<Integer> l = new ArrayList<>();
        for (int i : a)
            l.add(i);
        Collections.sort(l);
        for (int i = 0; i < a.length; i++)
            a[i] = l.get(i);
    }
 
    static void fill2D(char arr[][], char n) {
        for (char[] row : arr)
            Arrays.fill(row, n);
    }
 
    static class pair {
        int x;
        int y;
 
        pair(int i, int j) {
            x = i;
            y = j;
 
        }
 
        public String toString() {
            return x + " " + y;
        }
 
    }
 
    static class FastReader {
        BufferedReader br;
        StringTokenizer st;
        PrintWriter pw;
 
        public FastReader() {
            br = new BufferedReader(new InputStreamReader(System.in));
            pw = new PrintWriter(new OutputStreamWriter(System.out));
        }
 
        public FastReader(boolean b) {
            try {
                br = new BufferedReader(new FileReader("input.txt"));
                pw = new PrintWriter("output.txt");
 
            } catch (Exception e) {
 
            }
 
        }
 
        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
 
        int[] nextArray(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++)
                a[i] = nextInt();
            return a;
        }
 
        int nextInt() {
            return Integer.parseInt(next());
        }
 
        long nextLong() {
            return Long.parseLong(next());
        }
 
        double nextDouble() {
            return Double.parseDouble(next());
        }
 
        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
 
        void print(Object... objects) {
            for (int i = 0; i < objects.length; i++) {
                if (i != 0)
                    pw.print(' ');
                pw.print(objects[i]);
            }
        }
 
        void println(Object... objects) {
            for (int i = 0; i < objects.length; i++) {
                if (i != 0)
                    pw.print(' ');
                pw.print(objects[i]);
            }
            pw.println();
        }
 
        void viewArray1D(int a[]) {
            println(Arrays.toString(a));
        }
 
        void viewArray2D(int arr[][]) {
            for (int[] row : arr)
                viewArray1D(row);
        }
 
        void closer() {
            try {
                br.close();
                pw.flush();
                pw.close();
            } catch (Exception e) {
            }
        }
    }
}