[백준] 18352번 특정 거리의 도시 찾기 (파이썬)

https://www.acmicpc.net/problem/18352

BFS

import sys
from collections import deque

input = sys.stdin.readline

n, m, k, x = map(int, input().split())
graph = [[] for _ in range(n+1)]
for _ in range(m):
    a, b = map(int, input().split())
    graph[a].append(b)

visited = [False]*(n+1)
distance = [-1]*(n+1)

def bfs(graph, v):
    q = deque([v])
    visited[v] = True
    distance[v] = 0
    
    while q:
        v = q.popleft()
        for i in graph[v]:
            if not visited[i]:
                q.append(i)
                visited[i] = True
                distance[i] = distance[v] + 1
                    
bfs(graph, x)

result = []
for i in range(1, n+1):
    if distance[i] == k:
        result.append(i)
        
if result:
    print(*result, sep='\n')
else:
    print(-1)

다익스트라

import sys
import heapq

input = sys.stdin.readline

n, m, k, x = map(int, input().split())
graph = [[] for _ in range(n+1)]
for _ in range(m):
    a, b = map(int, input().split())
    graph[a].append(b)
    
INF = int(1e9)
distance = [INF]*(n+1)

def dijkstra(start):
    q = []
    heapq.heappush(q, (0, start))
    distance[start] = 0
    
    while q:
        dist, now = heapq.heappop(q)
        if distance[now] < dist:
            continue
        
        for i in graph[now]:
            cost = dist + 1
            if cost < distance[i]:
                distance[i] = cost
                heapq.heappush(q, (cost, i))

dijkstra(x)

result = []
for i in range(1, n+1):
    if distance[i] == k:
        result.append(i)
        
if result:
    print(*result, sep='\n')
else:
    print(-1)