41 lines
1020 B
Python
41 lines
1020 B
Python
import heapq
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import sys
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input = sys.stdin.readline
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def dijkstra(N, E, start) -> list[int]:
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heap = []
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distance = [10 ** 9 + 1 for _ in range(N + 1)]
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distance[start] = 0
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heapq.heappush(heap, (0, start,))
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while heap:
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cost, now, = heapq.heappop(heap)
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if distance[now] < cost:
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continue
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for new, weight in E[now]:
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new_cost = cost + weight
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if new_cost < distance[new]:
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distance[new] = new_cost
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heapq.heappush(heap, (new_cost, new))
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return distance
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def solve(N, M, E, iE, X):
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come = dijkstra(N, E, X)
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gone = dijkstra(N, iE, X)
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return max([come[i] + gone[i] for i in range(1, N + 1)])
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if __name__ == '__main__':
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N, M, X = map(int, input().split())
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E = {i: [] for i in range(1, N + 1)}
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iE = {i: [] for i in range(1, N + 1)}
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for _ in range(M):
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A, B, T = map(int, input().split())
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E[A].append((B, T))
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iE[B].append((A, T))
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print(solve(N, M, E, iE, X))
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