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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],
],
)
)
|