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Diffstat (limited to 'ancestors_node_acyclic_graph.py')
-rw-r--r-- | ancestors_node_acyclic_graph.py | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/ancestors_node_acyclic_graph.py b/ancestors_node_acyclic_graph.py new file mode 100644 index 0000000..b592e12 --- /dev/null +++ b/ancestors_node_acyclic_graph.py @@ -0,0 +1,71 @@ +# 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], + ], + ) + ) |