{ "data": { "question": { "questionId": "1431", "questionFrontendId": "2192", "boundTopicId": null, "title": "All Ancestors of a Node in a Directed Acyclic Graph", "titleSlug": "all-ancestors-of-a-node-in-a-directed-acyclic-graph", "content": "

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).

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You are also given a 2D integer array edges, where edges[i] = [fromi, toi] denotes that there is a unidirectional edge from fromi to toi in the graph.

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Return a list answer, where answer[i] is the list of ancestors of the ith node, sorted in ascending order.

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

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Example 1:

\n\"\"\n
\nInput: n = 8, edgeList = [[0,3],[0,4],[1,3],[2,4],[2,7],[3,5],[3,6],[3,7],[4,6]]\nOutput: [[],[],[],[0,1],[0,2],[0,1,3],[0,1,2,3,4],[0,1,2,3]]\nExplanation:\nThe above diagram represents the input graph.\n- Nodes 0, 1, and 2 do not have any ancestors.\n- Node 3 has two ancestors 0 and 1.\n- Node 4 has two ancestors 0 and 2.\n- Node 5 has three ancestors 0, 1, and 3.\n- Node 6 has five ancestors 0, 1, 2, 3, and 4.\n- Node 7 has four ancestors 0, 1, 2, and 3.\n
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Example 2:

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\nInput: n = 5, edgeList = [[0,1],[0,2],[0,3],[0,4],[1,2],[1,3],[1,4],[2,3],[2,4],[3,4]]\nOutput: [[],[0],[0,1],[0,1,2],[0,1,2,3]]\nExplanation:\nThe above diagram represents the input graph.\n- Node 0 does not have any ancestor.\n- Node 1 has one ancestor 0.\n- Node 2 has two ancestors 0 and 1.\n- Node 3 has three ancestors 0, 1, and 2.\n- Node 4 has four ancestors 0, 1, 2, and 3.\n
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Constraints:

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Most standard library headers are already included automatically for your convenience.

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For Map/TreeMap data structure, you may use sortedcontainers library.

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Note that Python 2.7 will not be maintained past 2020. For the latest Python, please choose Python3 instead.

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C# 10 with .NET 6 runtime

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