Added Monsters graph probl.em

cses/Graphs/Monster.cpp

@@ -0,0 +1,141 @@
+// Made by Daniel Diaz (@Danidiaztech)
+#include <bits/stdc++.h>
+using namespace std;
+
+#define endl '\n'
+#define fastInp cin.tie(0); cout.tie(0); ios_base::sync_with_stdio(0);
+#define forn(i, n) for (int i = 0; i < n; i++) // for in range in python
+#define FOR(i, a, b) for (int i = a; i < b; i++) // for in range in python
+#define int long long int
+#define double long double
+#define pb push_back
+#define ff first
+#define ss second
+#define mk make_pair
+
+typedef pair<int, int> pii;
+
+const int MAX = 1010;
+const int MIN = -MAX;
+const int INF = LLONG_MAX;
+const int MINF = LLONG_MIN;
+const int MOD = 1e9 + 7;
+
+int n,m;
+char g[MAX][MAX];
+// Distance from monsters
+int dism[MAX][MAX]; 
+// Distance from A
+int disa[MAX][MAX]; 
+
+
+char dir[] = {'L', 'R', 'U', 'D'};
+char rev[] = {'R', 'L', 'D', 'U'};
+int dirx[] = {0, 0, -1, 1};
+int diry[] = {-1, 1, 0, 0};
+map<char,int> mp = {{'L', 0}, {'R', 1}, {'U', 2}, {'D', 3}};
+
+bool is_valid(int x, int y){
+  if ((x >= 0 && x < n) && (y >= 0 && y < m) && (g[x][y] != '#') )
+    return true;
+  return false;
+}
+
+bool is_exit(int x, int y){
+  if (is_valid(x,y) && ( x == 0 || x == n - 1 ||  y == 0 || y == m - 1) && (g[x][y] == '.' || g[x][y] == 'A'))
+    return true;
+  return false;
+}
+
+void solve(){
+  // Another approach: Start with distance from Monsters
+  cin >> n >> m;
+  queue<pii> mo, a;
+  map<pii, pair<pii, char>> path;
+  int sx, sy, ex = -1, ey  =-1;
+  forn(i,n){
+    forn(j, m){
+      cin >> g[i][j];
+      dism[i][j] = INF;
+      if (g[i][j] == 'M'){
+        mo.push({i, j});
+        dism[i][j] = 0;
+      }
+      else if (g[i][j] == 'A'){
+        if (is_exit(i, j)){
+          cout << "YES\n0" << endl;
+          return;
+        }
+        a.push({i,j});
+        sx = i; sy = j;
+      }
+    } 
+  }
+
+  // BFS on monsters
+  while (!mo.empty() ){
+    pii u = mo.front(); 
+    mo.pop();
+    for (int i =0 ; i < 4; i++){
+      int x = u.ff + dirx[i], y = u.ss + diry[i];
+      if (is_valid(x, y) && dism[x][y] == INF){
+        dism[x][y] = dism[u.ff][u.ss] + 1;
+        mo.push({x, y});
+      }
+    }
+  }
+
+  // BFS on player
+  while (!a.empty()){
+    if (ex != -1) break;
+    pii u = a.front();
+    a.pop();
+    for (int i = 0; i < 4; i++){
+      int x = u.ff + dirx[i], y = u.ss + diry[i];
+      if (is_valid(x, y) && disa[x][y] == 0){
+        disa[x][y] = disa[u.ff][u.ss] + 1;
+        path[{x, y}] = {{u.ff, u.ss}, dir[i]};
+        if (dism[x][y] <= disa[x][y]){
+          continue;
+        }
+        if (is_exit(x, y)){
+          ex = x; ey = y;
+          break;
+        }
+        a.push({x, y});
+      }
+    }
+  } 
+
+  if (ex == -1){
+    cout << "NO" << endl; return;
+  }
+  vector<char> v;
+  // Reconstruct path
+  while (ex != sx || ey != sy){
+    v.pb(path[{ex, ey}].ss);
+    pii u = path[{ex,ey}].ff;
+    ex = u.ff;
+    ey = u.ss;
+  }
+  reverse(v.begin(), v.end());
+  cout << "YES\n" << v.size() << endl;
+  for (auto x: v) cout << x ;
+}
+
+int32_t main() {
+  fastInp;
+  #if LOCAL
+    freopen("input.txt", "r", stdin);
+    freopen("output.txt", "w", stdout);
+  #endif
+
+  int tc = 1;
+  // cin >> tc;
+
+  for (int t = 1; t <= tc; t++){
+    // cout << "Case #" << t << ": ";
+    solve();
+  }
+  return 0;
+}