Add la4509

Signed-off-by: Bruno Freitas Tissei <bft15@inf.ufpr.br>

algorithms/graph/bellman_ford.cpp

@@ -2,6 +2,8 @@
 ///
 /// Time: O(V * E)
 /// Space: O(V + E)
+///
+/// Status: Tested (LA4509)
 
 struct BellmanFord {
   struct Edge { int u, v, w; };
@@ -11,12 +13,17 @@ struct BellmanFord {
   vector<Edge> graph;
 
   BellmanFord(int N) : 
-    N(N), dist(N) {}
+    N(N), dist(N)
+  { init(); }
 
   void init() {
     fill(all(dist), inf);
   }
 
+  void add_edge(int u, int v, int w) {
+    graph.pb({ u, v, w });
+  }
+
   int run(int s, int d) {
     dist[s] = 0;
 
@@ -30,7 +37,7 @@ struct BellmanFord {
     // there is one
     for (auto e : graph)
       if (dist[e.u] != inf && 
-          dist[e.u] + w < dist[e.v])
+          dist[e.u] + e.w < dist[e.v])
         return -inf;
 
     return dist[d];

contests/Cadernaveis/LA4509.cpp

+#include <bits/stdc++.h>
+
+#define MAX 40
+#define EPS 1e-6
+#define MOD 1000000007
+#define inf 0x3f3f3f3f
+#define llinf 0x3f3f3f3f3f3f3f3f
+
+#define fi first
+#define se second
+#define pb push_back
+#define ende '\n'
+
+#define all(x) (x).begin(), (x).end()
+#define rall(x) (x).rbegin(), (x).rend()
+#define mset(x, y) memset(&x, (y), sizeof(x))
+
+using namespace std; 
+
+using ll = long long;
+using ii = pair<int,int>;
+
+int dx[] = {-1, 1, 0, 0};
+int dy[] = {0, 0, 1, -1};
+
+int mat[MAX][MAX];
+
+struct BellmanFord {
+  struct Edge { int u, v, w; };
+
+  int N;
+  vector<int> dist;
+  vector<Edge> graph;
+
+  BellmanFord(int N) : 
+    N(N), dist(N) 
+  { init(); }
+
+  void init() {
+    fill(all(dist), inf);
+  }
+
+  void add_edge(int u, int v, int w) {
+    graph.pb({ u, v, w });
+  }
+
+  int run(int s, int d) {
+    dist[s] = 0;
+
+    for (int i = 0; i < N; ++i)
+      for (auto e : graph)
+        if (dist[e.u] != inf && 
+            dist[e.u] + e.w < dist[e.v])
+          dist[e.v] = dist[e.u] + e.w;
+
+    for (auto e : graph)
+      if (dist[e.u] != inf && 
+          dist[e.u] + e.w < dist[e.v])
+        return -inf;
+
+    return dist[d];
+  }
+};
+
+int main() {
+  ios::sync_with_stdio(0);
+  cin.tie(0);
+
+  int r, c;
+  while (cin >> c >> r && (c || r)) {
+    mset(mat, 0);
+    BellmanFord bell(r*c);
+    
+    int g; cin >> g;
+    for (int i = 0; i < g; ++i) {
+      int x, y; cin >> x >> y;
+      mat[y][x] = 1;
+    }
+
+    int e; cin >> e;
+    for (int i = 0; i < e; ++i) {
+      int x1, y1; cin >> x1 >> y1;
+      int x2, y2; cin >> x2 >> y2;
+      int t; cin >> t;
+
+      bell.add_edge(y1 * c + x1, y2 * c + x2, t);
+      mat[y1][x1] = 1;
+    }
+
+    mat[r-1][c-1] = 1;
+    for (int i = 0; i < r; ++i)
+      for (int j = 0; j < c; ++j)
+        if (!mat[i][j])
+          for (int k = 0; k < 4; ++k) {
+            int di = i + dx[k];
+            int dj = j + dy[k];
+
+            if (di >= 0 && di < r && dj >= 0 && dj < c)
+              bell.add_edge(i*c + j, di*c + dj, 1);
+          }
+
+    int ans = bell.run(0, (r-1)*c + (c-1));
+
+    if (ans == -inf) cout << "Never" << ende;
+    else if (ans == inf) cout << "Impossible" << ende;
+    else cout << ans << ende;
+  }
+
+  return 0;
+}