g1501_1600.s1557_minimum_number_of_vertices_to_reach_all_nodes

Class Solution

java.lang.Object

g1501_1600.s1557_minimum_number_of_vertices_to_reach_all_nodes.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 Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
List<Integer>	findSmallestSetOfVertices(int n, List<List<Integer>> edges)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Solution

public Solution()

Method Detail

findSmallestSetOfVertices

public List<Integer> findSmallestSetOfVertices(int n,
                                               List<List<Integer>> edges)