[BOJ] 최소비용 구하기 / 골드5 / 30분

Author: jiyoung1814

jiyoung1814/boj_graph_min_cost.py

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+# import sys
+# sys.setrecursionlimit(10**6)
+#
+# def find_parent(parent, x):
+#     if parent[x] != x:
+#         parent[x] = find_parent(parent, parent[x])
+#     return parent[x]
+#
+# def union(parent, a, b):
+#     a = find_parent(parent, a)
+#     b = find_parent(parent, b)
+#
+#     if a < b:
+#         parent[b] = a
+#     else:
+#         parent[a] = b
+#
+#
+# city_num = int(sys.stdin.readline())
+# bus_num = int(sys.stdin.readline())
+#
+#
+# edges = []
+# parent = [i for i in range(city_num+1)]
+#
+# for bus in range(bus_num):
+#     a, b, cost = map(int, sys.stdin.readline().split())
+#     edges.append((cost, a, b))
+#
+# edges.sort()
+#
+#
+# for edge in edges:
+#     cost, a, b = edge
+#     if find_parent(parent, a) != find_parent(parent, b):
+#         union(parent, a, b)
+#
+#
+# start, end = map(int, sys.stdin.readline().split())
+#
+#
+# min_cost = 0
+# now_city = start
+#
+# while True:
+#     edge = next((edge for edge in edges if edge[1] == now_city), None)
+#
+#     if edge is None:
+#         break
+#
+#     cost, a, b = edge
+#
+#     min_cost += cost
+#     now_city = b
+#
+#     if now_city == end:
+#         break
+#
+# print(min_cost)
+
+import sys
+import heapq
+
+INF = float('inf')
+
+def dijkstra(start, end, n, adj_list):
+    dist = [INF] * (n+1)
+    dist[start] = 0
+
+    pq = []
+    heapq.heappush(pq, (0, start))  # (비용, 도시)
+
+    while pq:
+        now_cost, now_node = heapq.heappop(pq)
+
+        if now_cost > dist[now_node]: # 현재 비용이 큐에 있는 비용보다 작을 때만 갱신
+            continue
+
+        for new_node, new_cost in adj_list[now_node]:
+           new_cost = now_cost + new_cost
+
+           if new_cost < dist[new_node]:
+                dist[new_node] = new_cost
+                heapq.heappush(pq, (new_cost, new_node))
+
+    return dist[end]
+
+
+city_num = int(sys.stdin.readline())
+bus_num = int(sys.stdin.readline())
+
+adj_list = {i: [] for i in range(1, city_num + 1)}
+
+for _ in range(bus_num):
+    a, b, cost = map(int, sys.stdin.readline().split())
+    adj_list[a].append((b, cost))
+
+start, end = map(int, sys.stdin.readline().split())
+# city_num = 5
+# bus_num = 8
+# adj_list = {i: [] for i in range(1, city_num+1)}
+# edges = [
+#     (1, 2, 2),
+#     (1, 3, 3),
+#     (1, 4, 1),
+#     (1, 5, 10),
+#     (2, 4, 2),
+#     (3, 4, 1),
+#     (3, 5, 1),
+#     (4, 5, 3),
+# ]
+# start = 1
+# end = 5
+
+result = dijkstra(start, end, city_num, adj_list)
+print(result)