Dijkstra's algorithm

class Solution:
    def networkDelayTime(self, times: List[List[int]], n: int, k: int) -> int:
        adj = defaultdict(list)

        for u, v, w in times:
            adj[u].append((v, w))


        t = 0
        minH = [(0, k)]
        visited = set()

        while minH and len(visited) < n:
            w1, n1 = heapq.heappop(minH)

            if n1 in visited:
                continue

            visited.add(n1)
            t = max(t, w1)
            for n2, w2 in adj[n1]:
                if n2 not in visited:
                    heapq.heappush(minH, (w2 + w1, n2))

        return t if len(visited) == n else -1