Revise paste Untitled

#include <iostream>
#include <vector>
#include <queue>
#include <algorithm>
using namespace std;
int prev_step[1005][1005];
int main()
{
    ios_base::sync_with_stdio(false);
    cout.tie(0);
    cin.tie(0);

int n, m;
    cin >> n >> m;
    char mat[n][m];
    bool visited[n][m];
    int si, sj;
    int ei, ej;
    for(int i = 0; i < n; i++){
        for(int j = 0; j < m; j++){
            visited[i][j] = false;
            cin >> mat[i][j];
            if(mat[i][j] == 'A'){
                si = i;
                sj = j;
            }
            if(mat[i][j] == 'B') {
                ei = i;
                ej = j;
            }
        }
    }
 
    cout << endl;
 
    queue<int> q;
    q.push(si);
    q.push(sj);
    q.push(0);
    visited[si][sj] = true;
    int di[] = {1, -1, 0, 0};
    int dj[] = {0, 0, 1, -1};
    while(!q.empty()){
        int ci = q.front();
        q.pop();
        int cj = q.front();
        q.pop();
        int dist = q.front();
        q.pop();
        if(mat[ci][cj] == 'B'){
            break;
        }
      
        for(int i = 0; i < 4; i++){
            if(ci + di[i] < n and ci + di[i] >= 0 and cj + dj[i] < m and cj + dj[i] >= 0 and mat[ci + di[i]][cj + dj[i]] != '#' and !visited[ci + di[i]][cj + dj[i]]){
                
                q.push(ci + di[i]);
                q.push(cj + dj[i]);
                q.push(dist + 1);
                prev_step[ci + di[i]][cj + dj[i]] = i;
                visited[ci + di[i]][cj + dj[i]] = true;
            }
        }
    }
 
    if(visited[ei][ej]) {
        cout << "YES" << endl;
        pair<int, int> S = make_pair(si, sj);
        pair<int, int> E = make_pair(ei, ej);
        string result = "";
        while(E != S) {
            int p_cekor = prev_step[E.first][E.second];
            if(p_cekor == 0) {
                result += "D";
            }
            else if(p_cekor == 1) {
                result += "U";
            }
            else if(p_cekor == 2) {
                result += "R";
            }
            else {
                result += "L";
            }
            E = make_pair(E.first - di[p_cekor], E.second - dj[p_cekor]);
        }
        reverse(result.begin(), result.end());
        cout <<result.size() << endl <<  result << endl;
    }
    else {
        cout << "NO" << endl;
    }
    
    return 0;
 
}