출처 : 이코테
from collections import deque
n, m, k, x = map(int, input().split())
graph = [[] for _ in range(n+1)] #인덱스값 맞추기 위해 n+1
print(graph) # [[], [], [], [], []]
for _ in range(m):
a, b = map(int, input().split())
graph[a].append(b)
print(graph) # [[], [2, 3], [3, 4], [], []]
distance = [-1] * (n+1)
distance[x] = 0
print(distance) # [-1, 0, -1, -1, -1]
q = deque([x])
while q:
now = q.popleft() # 1, 3, 2
for next_node in graph[now]: # next_node = [2,3], [3,4]
if distance[next_node] == -1:
distance[next_node] = distance[now] + 1
q.append(next_node)
check = False
for i in range(1, n+1):
if distance[i] == k:
print(i)
check = True
if check == False:
print(-1)
Hi