def can_jump_all_cells(N, steps):from collections import defaultdict, deque# 构建图的邻接表graph = defaultdict(list)for u, v in steps:graph[u].append(v)# 记录每个格子的入度in_degree = [0] * Nfor u, v in steps:in_degree[v] += 1# 找到所有入度为0的格子（起始格子）queue = deque([i for i in range(N) if in_degree[i] == 0])visited = set(queue)# BFS遍历while queue:u = queue.popleftfor v in graph[u]:if v not in visited:visited.add(v)queue.append(v)# 如果所有格子都被访问过，则输出yes，否则输出noreturn "yes" if len(visited) == N else "no"# 读取输入N = int(input.strip)steps = while True:try:line = input.stripif line:step = list(map(int, line.split))steps.append(step)else:breakexcept EOFError:break# 计算并输出结果print(can_jump_all_cells(N, steps))摘要：def can_jump_all_cells(N, steps):from collections import defaultdict, deque# 构建图的邻接表graph = defaultdict(list)for u, v in steps:gra
来源：稻草熊游戏