[BOJ] 1238 파티 (G3)

Author: jihostudy

김지호/6주차/260207.py

@@ -0,0 +1,68 @@
+# https://www.acmicpc.net/problem/1238
+# 파티, 골드3
+
+import sys
+import copy
+from collections import deque, defaultdict
+from typing import List
+sys.stdin = open('../../../input.txt', 'r')
+
+inputs = list(map(int,input().split(" ")))
+
+# N(마을 개수), M(단방향 도로 개수), X(목적지 마을 번호)
+N = int(inputs[0])
+M = int(inputs[1])
+X = int(inputs[2]) - 1
+INF = float('inf')
+
+graph = [[INF] * N for _ in range(N)]
+reversed_graph = [[INF] * N for _ in range(N)]
+for _ in range(M):
+  inputs = list(map(int,input().split(" ")))
+  start  = int(inputs[0])-1
+  end  = int(inputs[1])-1
+  dist  = int(inputs[2])
+  graph[start][end] = dist # start -> end 거리 dist
+  reversed_graph[end][start] = dist # start -> end 거리 dist
+
+for i in range(N):
+  graph[i][i] = 0
+  reversed_graph[i][i] = 0
+
+def print_2d_arr(array):
+  for arr in array:
+    print(arr)
+
+def getMinNode(distance,visited,N):
+  minNode = -1
+  minDist = INF
+  for node in range(N):
+    if(not visited[node] and distance[node] < minDist):
+      minNode = node
+      minDist = distance[node]
+  return minNode
+
+# start에서 출발하는 최단거리 
+def dijkstra(graph,start,N):
+  visited = [False] * N
+  distance = graph[start]
+  
+  visited[start] = True
+  
+  for _ in range(N):
+    node = getMinNode(distance,visited,N)
+    
+    visited[node] = True
+    for i in range(N):
+      if not visited[i] and distance[i] > graph[node][i] + distance[node]:
+        distance[i] = graph[node][i] + distance[node]
+  
+  return distance
+
+go_distance = dijkstra(reversed_graph,X,N)
+come_distance = dijkstra(graph,X,N)
+
+answer = -INF # 최장거리 구하기
+for i in range(N):
+  answer = max(answer,go_distance[i] + come_distance[i])
+print(answer)