2192 - All Ancestors of a Node in a Directed Acyclic Graph.

Medium

You are given a positive integer n representing the number of nodes of a Directed Acyclic Graph (DAG). The nodes are numbered from 0 to n - 1 ( inclusive ).

You are also given a 2D integer array edges, where <code>edgesi = from_i, to_i</code> denotes that there is a unidirectional edge from <code>from_i</code> to <code>to_i</code> in the graph.

Return a list answer, where answer[i] is the list of ancestors of the <code>i^th</code> node, sorted in ascending order.

A node u is an ancestor of another node v if u can reach v via a set of edges.

Example 1:

Input: n = 8, edgeList = [0,3,0,4,1,3,2,4,2,7,3,5,3,6,3,7,4,6]

Output: [ [],[],[],0,1,0,2,0,1,3,0,1,2,3,4,0,1,2,3]

Explanation:

The above diagram represents the input graph.

• Nodes 0, 1, and 2 do not have any ancestors.

• Node 3 has two ancestors 0 and 1.

• Node 4 has two ancestors 0 and 2.

• Node 5 has three ancestors 0, 1, and 3.

• Node 6 has five ancestors 0, 1, 2, 3, and 4.

• Node 7 has four ancestors 0, 1, 2, and 3.

Example 2:

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

Output: [ [],0,0,1,0,1,2,0,1,2,3]

Explanation:

The above diagram represents the input graph.

• Node 0 does not have any ancestor.

• Node 1 has one ancestor 0.

• Node 2 has two ancestors 0 and 1.

• Node 3 has three ancestors 0, 1, and 2.

• Node 4 has four ancestors 0, 1, 2, and 3.

Constraints:

• 1 <= n <= 1000

• 0 <= edges.length <= min(2000, n * (n - 1) / 2)

• edges[i].length == 2

• <code>0 <= from_i, to_i<= n - 1</code>

• <code>from_i != to_i</code>

• There are no duplicate edges.

• The graph is directed and acyclic.