Abandoned warehouse

input/code.cpp: In function 'int main()':
input/code.cpp:56:9: warning: unused variable 'found' [-Wunused-variable]
   56 |    bool found = false;
      |         ^~~~~

#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <queue>

using namespace std;

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

   // freopen("input.txt", "r", stdin); // TODO: REMOVE THIS YOU STUPID ****

   int n, m;
   cin >> n >> m;

   auto a = -1;
   auto b = -1;
   vector<vector<int>> dirs(n*m);
   string map = "";
   for (int i = 0; i < n; i++) {
      string line;
      cin >> line;
      map += line;
   }
   for (int i = 0; i < n*m; i++) {
      auto elem = map[i];
      if (elem == '#') continue;

      if (elem == 'A') a = i;
      else if (elem == 'B') b = i;
      // top
      if (i - m >= 0) {
         char te = map[i-m];
         if (te != '#') {
            dirs[i].push_back(i-m);
            dirs[i-m].push_back(i);
         }
      }
      // left, same line
      if ((i-1)/m == i/m && i - 1 >= 0) {
         char te = map[i-1];
         if (te != '#') {
            dirs[i].push_back(i-1);
            dirs[i-1].push_back(i);
         }
      }
   }
   vector<bool> visited(n*m, false);
   vector<int> parent(n*m, -1);
   queue<int> q;

   visited[a] = true;
   q.push(a);
   bool found = false;
   while (!q.empty()) {
      int s = q.front(); q.pop();
      for (auto &u : dirs[s]) {
         if (visited[u]) continue;
         visited[u] = true;
         parent[u] = s;
         if (u == b) break;
         q.push(u);
      }
   }
   if (parent[b] == -1) {
      cout << "NO";
      return 0;
   }
   string ans = "";
   int i = b;
   while (i != a) {
      int par = parent[i];
      // from left
      if (par == i - 1) {
         ans += "R";
      } else if (par == i + 1) {
         // from right;
         ans += "L";
      } else if (par == i - m) {
         // from top
         ans += "D";
      } else ans += "U";
      i = par;
   }
   reverse(ans.begin(), ans.end());
   cout << "YES\n" << ans.length() << "\n" << ans;
}

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: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED