bellman

programmation_dynamique/bellman/main.py

@@ -0,0 +1,28 @@
+def bellman_ford(graphe, sommet):
+    distance = {sommet: float("inf") for sommet in graphe}
+    distance[sommet] = 0
+
+    for i in range(len(graphe) - 1):
+        for u in graphe:
+            for v, coef in graphe[u]:
+                if distance[u] + coef < distance[v]:
+                    distance[v] = distance[u] + coef
+
+    for u in graphe:
+        for v, coef in graphe[u]:
+            if distance[u] + coef < distance[v]:
+                raise ValueError("Cycle négatif détecté")
+
+    return distance
+
+
+if __name__ == "__main__":
+    graphe = {
+        "A": [("G", 8), ("H", 4)],
+        "G": [("H", 1), ("L", 2)],
+        "H": [("L", 5), ("E", 7)],
+        "L": [("E", -2)],
+        "E": [],
+    }
+    distances = bellman_ford(graphe, "A")
+    print(distances)