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Diffstat (limited to 'count_num_good_nodes.py')
-rw-r--r-- | count_num_good_nodes.py | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/count_num_good_nodes.py b/count_num_good_nodes.py new file mode 100644 index 0000000..fa876f9 --- /dev/null +++ b/count_num_good_nodes.py @@ -0,0 +1,77 @@ +# 3249. Count the Number of Good Nodes +from collections import defaultdict + +""" +there is an undirected tree with 'n' nodes labeled from 0 to 'n - 1', and +rooted at node 0. you are given a 2d integer array 'edges' of length 'n - 1' +where 'edges[i] = [a_i, b_i]' indicates that there is an edge between nodes +'a_i' and 'b_i' in the tree. a node is good if all the subtrees rooted at is +children have the same size. return the number of good nodes in the given +tree. a subtree of 'treeName' is a tree consisting of a node in 'treeName' +and all of its descendants. +""" + + +class Solution(object): + def countGoodNodes(self, edges): + """ + :type edges: List[List[int]] + :rtype: int + """ + n = len(edges) + 1 + graph = defaultdict(list) + subtree_size = [0] * n + + def dfs(curr, parent): + n = 1 + for i in graph[curr]: + if i != parent: + n += dfs(i, curr) + subtree_size[curr] = n + return n + + for u, v in edges: + graph[u].append(v) + graph[v].append(u) + dfs(0, -1) + ans = 0 + for i in range(n): + flag, prev = True, -1 + for j in graph[i]: + if subtree_size[j] < subtree_size[i]: + if prev == -1: + prev = subtree_size[j] + elif prev != subtree_size[j]: + flag = False + break + if flag: + ans += 1 + return ans + + +if __name__ == "__main__": + obj = Solution() + print(obj.countGoodNodes(edges=[[0, 1], [0, 2], [1, 3], [1, 4], [2, 5], [2, 6]])) + print( + obj.countGoodNodes( + edges=[[0, 1], [1, 2], [2, 3], [3, 4], [0, 5], [1, 6], [2, 7], [3, 8]] + ) + ) + print( + obj.countGoodNodes( + edges=[ + [0, 1], + [1, 2], + [1, 3], + [1, 4], + [0, 5], + [5, 6], + [6, 7], + [7, 8], + [0, 9], + [9, 10], + [9, 12], + [10, 11], + ] + ) + ) |