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sum-of-distances-in-tree.py 1.08 KB
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Allen Liu 提交于 7年前 . add complexity
# Time: O(n)
# Space: O(n)
import collections
class Solution(object):
def sumOfDistancesInTree(self, N, edges):
"""
:type N: int
:type edges: List[List[int]]
:rtype: List[int]
"""
def dfs(graph, node, parent, count, result):
for nei in graph[node]:
if nei != parent:
dfs(graph, nei, node, count, result)
count[node] += count[nei]
result[node] += result[nei]+count[nei]
def dfs2(graph, node, parent, count, result):
for nei in graph[node]:
if nei != parent:
result[nei] = result[node]-count[nei] + \
len(count)-count[nei]
dfs2(graph, nei, node, count, result)
graph = collections.defaultdict(list)
for u, v in edges:
graph[u].append(v)
graph[v].append(u)
count = [1] * N
result = [0] * N
dfs(graph, 0, None, count, result)
dfs2(graph, 0, None, count, result)
return result
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