Abandoned warehouse

#include "bits/stdc++.h"

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;

#define F first
#define S second
#define PB push_back
#define MP make_pair

#define REP(i,a,b) for (int i = a; i < b; i++)


int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);

    int n, m;
    cin >> n >> m;
    // vector<int> nodes(n);
    vector<int> map(n*m);
    vector<vector<int>> edges(n*m);
    int start= 0;
    int goal = 0;

    REP(i, 0, n) {
        REP(j, 0, m) {
            char a;
            cin >> a;

            if(a == 'A') {
                start = i*m+j;
                map[i*m + j] = '.';
                if(i > 0 && map[(i-1)*m + j] == '.') {
                    edges[(i-1)*m + j].PB((i)*m + j);
                    edges[(i)*m + j].PB((i-1)*m + j);
                } 
                if(j > 0 && map[(i)*m + j - 1] == '.') {
                    edges[(i)*m + j-1].PB((i)*m + j);
                    edges[(i)*m + j].PB((i)*m + j-1);
                }
            } else if(a == 'B') {
                goal = i*m+j;
                map[i*m + j] = '.';
                if(i > 0 && map[(i-1)*m + j] == '.') {
                    edges[(i-1)*m + j].PB((i)*m + j);
                    edges[(i)*m + j].PB((i-1)*m + j);
                } 
                if(j > 0 && map[(i)*m + j - 1] == '.') {
                    edges[(i)*m + j-1].PB((i)*m + j);
                    edges[(i)*m + j].PB((i)*m + j-1);
                }
            } else if(a == '.') {
                map[i*m + j] = '.';
                if(i > 0 && map[(i-1)*m + j] == '.') {
                    edges[(i-1)*m + j].PB((i)*m + j);
                    edges[(i)*m + j].PB((i-1)*m + j);
                } 
                if(j > 0 && map[(i)*m + j - 1] == '.') {
                    edges[(i)*m + j-1].PB((i)*m + j);
                    edges[(i)*m + j].PB((i)*m + j-1);
                }
            } else {
                map[i*m + j] = '#';
            }
        }
    }

    vector<bool> visited(n*m);
    stack<char> path;
    queue<int> q;
    vector<int> distance(n*m,-1);
    q.push(start);
    visited[start] = true;
    distance[start] = 0;
    
    vector<int> parents(n*m, -1);

    while(!q.empty()) {
        int l = q.front(); q.pop();

        for(auto e: edges[l]) {
            if(visited[e]) continue;
            parents[e] = l;
            distance[e] = distance[l] + 1;
            q.push(e);
           
            visited[e] = true;
        }
    }
    int node = goal;
    path.push(node);

    if(distance[goal] == -1) {
        std::cout << "NO"<< "\n";
    } else {
        std::cout << "YES" << "\n" << distance[goal] << "\n";
        while(parents[node] != -1) {
            path.push(parents[node]);
            node = parents[node];
        }
        int a, b = path.top(); path.pop();

        while(!path.empty()) {
            a = b;
            b = path.top(); path.pop();
            int d = a-b;
            //std::cout << d << " HERE" << "\n";
            if(d == -1) {
                std::cout << "R";
            } else if(d == 1) {
                std::cout << "L";
            } else if(d > 0) {
                std::cout << "U";
            } else {
                std::cout << "D";
            }
        }
        std::cout << "\n";
    }

    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: WRONG ANSWER

Test 8

Verdict: WRONG ANSWER

Test 9

Verdict: WRONG ANSWER

Test 10

Verdict: WRONG ANSWER

Test 11

Verdict: WRONG ANSWER

Test 12

Verdict: WRONG ANSWER

Test 13

Verdict: WRONG ANSWER

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: WRONG ANSWER