# 18.05.2023 [1557. Minimum Number of Vertices to Reach All Nodes]

18.05.2023

1557. Minimum Number of Vertices to Reach All Nodes medium
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Problem TLDR

Find all starting nodes in graph.

Intuition

Count nodes that have no incoming connections.

Approach

• we can use subtract operation in Kotlin

Complexity

• Time complexity:
  O(n)O(n)

• Space complexity:
  O(n)O(n)

Code

fun findSmallestSetOfVertices(n: Int, edges: List<List<Int>>): List<Int> =
    (0 until n) - edges.map { it[1] }