题目：原题链接（中等）
标签：树、图、深度优先搜索、广度优先搜索
解法 | 时间复杂度 | 空间复杂度 | 执行用时 |
Ans 1 (Python) | O ( E ) | O ( E ) | 220ms (75.00%) |
Ans 2 (Python) | |||
Ans 3 (Python) |
解法一（深度优先搜索）：
# 生成无向图中边的集合表示
def build_graph_set(edges):
graph = collections.defaultdict(set)
for edge in edges:
graph[edge[0]].add(edge[1])
graph[edge[1]].add(edge[0])
return graph
class Solution:
def __init__(self):
self.ans = 0
self.graph = collections.defaultdict(set)
def treeDiameter(self, edges: List[List[int]]) -> int:
if not edges:
return 0
self.graph = build_graph_set(edges)
self.dfs(0, -1)
return self.ans
def dfs(self, node, parent):
lengths = [self.dfs(child, node) for child in self.graph[node] if child != parent]
if len(lengths) == 0:
return 0
elif len(lengths) == 1:
self.ans = max(self.ans, lengths[0] + 1)
return lengths[0] + 1
else:
n1, n2 = heapq.nlargest(2, lengths)
self.ans = max(self.ans, n1 + n2 + 2)
return max(n1, n2) + 1
