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1557. Minimum Number of Vertices to Reach All Nodes

https://leetcode.com/problems/minimum-number-of-vertices-to-reach-all-nodes/

Python​

Outdegree Difference​

  • 能夠透過其他節點到達的節點(edge outdegree)都可以視為reachable
  • 所有節點與edge outdegree的差集，即是至少要使用的出發點
class Solution:
    def findSmallestSetOfVertices(self, n: int, edges: List[List[int]]) -> List[int]:
        nodes = set(range(n))
        outdegree = set([edge[1] for edge in edges])

        return list(nodes - outdegree)