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-rw-r--r--ancestors_node_acyclic_graph.py71
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+# 2192. All Ancestors of a Node in a Directed Acyclic Graph
+from collections import defaultdict
+
+"""
+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' inclusively.
+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. return a list 'answer' where 'answer[i]' is the list of ancestors of
+the i'th 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.
+"""
+
+
+class Solution(object):
+ def getAncestors(self, n, edges):
+ """
+ :type n: int
+ :type edges: List[List[int]]
+ :rtype: List[List[int]]
+ """
+ direct_child = defaultdict(list)
+ ans = [[] for _ in range(n)]
+ for x,y in edges:
+ direct_child[x].append(y)
+ def dfs(x, curr):
+ for i in direct_child[curr]:
+ if ans[i] ans and ans[i][-1] == x:
+ continue
+ ans[i].append(x)
+ dfs(x, i)
+ for i in range(n):
+ dfs(i, i)
+ return ans
+
+
+if __name__ == "__main__":
+ obj = Solution()
+ print(
+ obj.getAncestors(
+ n=8,
+ edgeList=[
+ [0, 3],
+ [0, 4],
+ [1, 3],
+ [2, 4],
+ [2, 7],
+ [3, 5],
+ [3, 6],
+ [3, 7],
+ [4, 6],
+ ],
+ )
+ )
+ print(
+ obj.getAncestors(
+ n=5,
+ edgeList=[
+ [0, 1],
+ [0, 2],
+ [0, 3],
+ [0, 4],
+ [1, 2],
+ [1, 3],
+ [1, 4],
+ [2, 3],
+ [2, 4],
+ [3, 4],
+ ],
+ )
+ )