init

1C.py

@@ -0,0 +1,33 @@
+N, M = map(int, input().split())
+adj = [[] for i in range(N+1)]
+for i in range(M):
+    u, v  = map(int, input().split())
+    adj[u].append(v)
+color = [0]*(N+1) # 0-нет цвета, 1 - обработка, 2 - отмечена и мы закончили
+parent = [0]*(N+1)
+for i in range(1, N+1):
+    if color[i] == 0:
+        stack = [i]
+        while stack:
+            u = stack.pop()
+            if color[u] == 0:
+                color[u] = 1
+                stack.append(u)
+                for v in adj[u]:
+                    if color[v] == 0:
+                        stack.append(v)
+                        parent[v] = u
+                    elif color[v] == 1 :
+                        cycle = [v]
+                        curr = u
+                        while curr != v:
+                            cycle.append(curr)
+                            curr = parent[curr]
+                        print(len(cycle))
+                        print(*(cycle[::-1]))
+                        exit()
+            elif color[u] == 1:
+                color[u] = 2
+
+print("-1")
+