Package g1501_1600.s1557_minimum_number_of_vertices_to_reach_all_nodes

Class Solution

  • public class Solution
extends Object
    1557 - Minimum Number of Vertices to Reach All Nodes.

    Medium

    Given a** directed acyclic graph** , with n vertices numbered from 0 to n-1, and an array edges where edges[i] = [fromi, toi] represents a directed edge from node fromi to node toi.

    Find the smallest set of vertices from which all nodes in the graph are reachable. It’s guaranteed that a unique solution exists.

    Notice that you can return the vertices in any order.

    Example 1:

    Input: n = 6, edges = [[0,1],[0,2],[2,5],[3,4],[4,2]]

    Output: [0,3]

    Explanation: It’s not possible to reach all the nodes from a single vertex. From 0 we can reach [0,1,2,5]. From 3 we can reach [3,4,2,5]. So we output [0,3].

    Example 2:

    Input: n = 5, edges = [[0,1],[2,1],[3,1],[1,4],[2,4]]

    Output: [0,2,3]

    Explanation: Notice that vertices 0, 3 and 2 are not reachable from any other node, so we must include them. Also any of these vertices can reach nodes 1 and 4.

    Constraints:

    • 2 <= n <= 10^5
    • 1 <= edges.length <= min(10^5, n * (n - 1) / 2)
    • edges[i].length == 2
    • 0 <= fromi, toi < n
    • All pairs (fromi, toi) are distinct.

    • Constructor Detail

      • Solution

        public Solution()