298 - Binary Tree Longest Consecutive Sequence
Written on October 29, 2015
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Given a binary tree, find the length of the longest consecutive sequence path. The path refers to any sequence of nodes from some starting node to any node in the tree along the parent-child connections. The longest consecutive path need to be from parent to child (cannot be the reverse).
class Solution:
def longestConsecutive(self, root: TreeNode) -> int:
ret = [0]
def helper(node):
if not node:
return 0
local_max = 1
left = helper(node.left)
right = helper(node.right)
if node.left and node.left.val == node.val + 1:
local_max = max(local_max, left + 1)
if node.right and node.right.val == node.val + 1:
local_max = max(local_max, right + 1)
ret[0] = max(ret[0], local_max)
return local_max
helper(root)
return ret[0]
class Solution:
def longestConsecutive(self, root: TreeNode) -> int:
if not root:
return 0
stack = [[root, 1]]
ret = 0
while stack:
node, count = stack.pop()
if node.left:
stack.append([node.left, count + 1 if node.left.val == node.val + 1 else 1])
if node.right:
stack.append([node.right, count + 1 if node.right.val == node.val + 1 else 1])
ret = max(ret, count)
return ret