fork download
copy 
  1. #include <iostream>
  2. #include <vector>
  3. #include <queue>
  4. #include <string>
  5. #include <algorithm>
  6.  
  7. using namespace std;
  8.  
  9. int n, m;
  10. vector<string> grid;
  11. vector<vector<int>> distM, distA;
  12. vector<vector<pair<int, int>>> parent;
  13. vector<vector<char>> dir;
  14.  
  15. // Direction arrays for Up, Down, Left, Right
  16. int dr[] = {-1, 1, 0, 0};
  17. int dc[] = {0, 0, -1, 1};
  18. char move_dir[] = {'U', 'D', 'L', 'R'};
  19.  
  20. // Function to check if a cell is valid to move into
  21. bool isValid(int r, int c) {
  22.     return (r >= 0 && r < n && c >= 0 && c < m && grid[r][c] != '#');
  23. }
  24.  
  25. int main() {
  26.     // Optimize input/output operations
  27.     ios_base::sync_with_stdio(false);
  28.     cin.tie(NULL);
  29.  
  30.     if (!(cin >> n >> m)) return 0;
  31.  
  32.     grid.resize(n);
  33.     distM.assign(n, vector<int>(m, 1e9)); // Initialize with a large number (infinity)
  34.     distA.assign(n, vector<int>(m, 1e9));
  35.     parent.assign(n, vector<pair<int, int>>(m, {-1, -1}));
  36.     dir.assign(n, vector<char>(m, ' '));
  37.  
  38.     queue<pair<int, int>> qM, qA;
  39.     pair<int, int> startA;
  40.  
  41.     // Read the grid and find the starting positions of the player and all monsters
  42.     for (int i = 0; i < n; i++) {
  43.         cin >> grid[i];
  44.         for (int j = 0; j < m; j++) {
  45.             if (grid[i][j] == 'M') {
  46.                 qM.push({i, j});
  47.                 distM[i][j] = 0;
  48.             } else if (grid[i][j] == 'A') {
  49.                 startA = {i, j};
  50.                 qA.push({i, j});
  51.                 distA[i][j] = 0;
  52.             }
  53.         }
  54.     }
  55.  
  56.     // Step 1: Multi-source BFS for all monsters
  57.     while (!qM.empty()) {
  58.         auto [r, c] = qM.front();
  59.         qM.pop();
  60.  
  61.         for (int i = 0; i < 4; i++) {
  62.             int nr = r + dr[i];
  63.             int nc = c + dc[i];
  64.  
  65.             // If the cell is valid and hasn't been visited by a monster yet
  66.             if (isValid(nr, nc) && distM[nr][nc] == 1e9) {
  67.                 distM[nr][nc] = distM[r][c] + 1;
  68.                 qM.push({nr, nc});
  69.             }
  70.         }
  71.     }
  72.  
  73.     // Step 2: BFS for the Player 'A'
  74.     bool possible = false;
  75.     pair<int, int> end_pos = {-1, -1};
  76.  
  77.     while (!qA.empty()) {
  78.         auto [r, c] = qA.front();
  79.         qA.pop();
  80.  
  81.         // If 'A' has reached the boundary of the grid safely
  82.         if (r == 0 || r == n - 1 || c == 0 || c == m - 1) {
  83.             possible = true;
  84.             end_pos = {r, c};
  85.             break;
  86.         }
  87.  
  88.         for (int i = 0; i < 4; i++) {
  89.             int nr = r + dr[i];
  90.             int nc = c + dc[i];
  91.  
  92.             if (isValid(nr, nc) && distA[nr][nc] == 1e9) {
  93.                 // 'A' can only step here if they get there faster than any monster
  94.                 if (distA[r][c] + 1 < distM[nr][nc]) {
  95.                     distA[nr][nc] = distA[r][c] + 1;
  96.                     parent[nr][nc] = {r, c};    // Track where we came from
  97.                     dir[nr][nc] = move_dir[i];  // Track what move we made to get here
  98.                     qA.push({nr, nc});
  99.                 }
  100.             }
  101.         }
  102.     }
  103.  
  104.     // Step 3: Print result and reconstruct the path
  105.     if (possible) {
  106.         cout << "YES\n";
  107.         string path = "";
  108.         int r = end_pos.first;
  109.         int c = end_pos.second;
  110.  
  111.         // Backtrack from the exit to the start point
  112.         while (r != startA.first || c != startA.second) {
  113.             path += dir[r][c];
  114.             auto p = parent[r][c];
  115.             r = p.first;
  116.             c = p.second;
  117.         }
  118.  
  119.         // Reverse the path since we built it backwards
  120.         reverse(path.begin(), path.end());
  121.         cout << path.length() << "\n";
  122.         cout << path << "\n";
  123.     } else {
  124.         cout << "NO\n";
  125.     }
  126.  
  127.     return 0;
  128. }
Success #stdin #stdout 0.01s 5316KB
comments (?)
stdin
copy 
5 8
########
#M..A..#
#.#.M#.#
#M#..#..
#.######
stdout
copy 
YES
5
RRDDR
https://ideone.com/AMJnDq
language:
C++ (gcc 8.3)
created:
11 hours ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!