Update courses.py

LabMD_3/courses.py

@@ -1 +1,56 @@
 
+from collections import defaultdict, deque
+class Solution:
+    def solve(self, edges):
+        graph = defaultdict(list)
+        weights = {}
+        max_weight = 0
+        N = 0
+        for u, v, w in edges:
+            graph[u].append(v)
+            graph[v].append(u)
+            weights[u, v] = w
+            weights[v, u] = w
+            N = max(N, u + 1, v + 1)
+            max_weight = max(max_weight, w)
+        def bfs(root, weight_cap):
+            target = N - 1
+            Q = deque([(root, 0, 0)])
+            visited = [False] * N
+            visited[0] = True
+            while Q:
+                v, d, current_weight = Q.pop()
+                if v == N - 1:
+                    return d, current_weight
+                for w in graph[v]:
+                    if visited[w]:
+                        continue
+                    new_weight = weights[v, w]
+                    if new_weight <= weight_cap:
+                        visited[w] = True
+                        Q.appendleft((w, d + 1, max(current_weight, new_weight)))
+            return -1, -1
+        result = float("inf")
+        while max_weight >= 0:
+            d, weight = bfs(0, max_weight)
+            if d >= 0:
+                result = min(result, d * weight)
+                max_weight = weight - 1
+            else:
+                break
+        return result if result < float("inf") else -1
+
+ob = Solution()
+graph = [
+    [0, 1, 1],
+    [1, 2, 1],
+    [2, 3, 1],
+    [3, 4, 1]
+]
+
+value = (ob.solve(graph))
+
+if value == len(graph):
+    print("possible")
+else:
+    print("impossible")