Leetcode 3604. Minimum Time to Reach Destination in Directed Graph

• Leetcode 3604. Minimum Time to Reach Destination in Directed Graph
  • 1. 解题思路
  • 2. 代码实现

• 题目链接：3604. Minimum Time to Reach Destination in Directed Graph

1. 解题思路

这一题思路上就是一个广度优先遍历，我们不断考察当前时间点以及位置的情况下，下一个点可行的位置，然后考察最近的时间点能够到达的位置，遍历全部可能性直至达到目标位置即可。

2. 代码实现

给出python代码实现如下：

class Solution:
    def minTime(self, n: int, edges: List[List[int]]) -> int:
        graph = defaultdict(list)
        for u, v, st, ed in edges:
            graph[u].append((v, st, ed))

        q = [(0, 0)]
        seen = set()
        while q:
            t, u = heapq.heappop(q)
            if u == n-1:
                return t

            if u in seen:
                continue
            seen.add(u)
            
            for v, st, ed in graph[u]:
                if t > ed or v in seen:
                    continue
                heappush(q, (max(t+1, st+1), v))
        return -1

提交代码评测得到：耗时234ms，占用内存72.14MB。