[BOJ] 1504 특정한 최단 경로 (G4)

Author: jihostudy

김지호/6주차/260205.py

@@ -0,0 +1,75 @@
+# https://www.acmicpc.net/problem/1504
+# 특정한 최단 경로, 골드4
+
+import sys
+import copy
+from collections import deque, defaultdict
+from typing import List
+sys.stdin = open('../../../input.txt', 'r')
+
+N, E = map(int,input().split(" ")) # N(정점 개수), E(간선 개수)
+
+# 다익스트라 문제
+INF = float('inf')
+graph = [[INF] * N for _ in range(N)]
+
+for i in range(N):
+  graph[i][i] = 0
+
+for _ in range(E):
+  start,end,dist = map(int,input().split(" "))
+  graph[start-1][end-1] = dist
+  graph[end-1][start-1] = dist
+
+# 거쳐야 하는 점들
+inputs = list(map(int,input().split(" ")) )
+x1 = inputs[0]-1
+x2 = inputs[1]-1
+
+# startNode -> endNode
+startNode = 1-1
+endNode = N-1
+
+# 방문할 수 잇는 노드 중에 제일 가까운 노드
+def getMinNode(distance, visited, N):
+  minNode = -1
+  minDistance = INF
+  for i in range(N):
+    if not visited[i] and minDistance > distance[i]:
+      minNode = i
+      minDistance = distance[i]
+  return minNode
+
+
+def dijkstra(graph,N,start,end):
+  visited = [False] * N
+  distance = graph[start] # 최신 거리
+  
+  visited[start] = True
+  
+  for _ in range(N):
+    node = getMinNode(distance, visited, N)
+  
+    visited[node] = True
+      
+    for index, dist in enumerate(graph[node]):
+      if not visited[index] and distance[index] > distance[node] + dist:
+        distance[index] = distance[node] + dist
+  # print(f"{start} > {end} 최단거리 구하기")
+  # print(distance)
+  # print()
+  return distance[end]
+
+# 2가지 거리를 계싼
+common = dijkstra(graph,N,x1,x2)
+answer1 = dijkstra(graph,N,startNode,x1) + dijkstra(graph,N,x2,endNode)
+answer2 = dijkstra(graph,N,startNode,x2) + dijkstra(graph,N,x1,endNode)
+
+answer = min(answer1, answer2) + common
+if answer == INF:
+  print(-1)
+else:
+  print(answer)
+# print(common + answer1)
+# print(common + answer2)
+