tree

Author: idf

298 Binary Tree Longest Consecutive Sequence.py

@@ -0,0 +1,79 @@
+"""
+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).
+
+For example,
+   1
+    \
+     3
+    / \
+   2   4
+        \
+         5
+Longest consecutive sequence path is 3-4-5, so return 3.
+   2
+    \
+     3
+    /
+   2
+  /
+ 1
+Longest consecutive sequence path is 2-3,not3-2-1, so return 2.
+
+"""
+__author__ = 'Daniel'
+
+
+class TreeNode(object):
+    def __init__(self, x):
+        self.val = x
+        self.left = None
+        self.right = None
+
+
+class Solution(object):
+    def __init__(self):
+        self.maxa = 0
+
+    def longestConsecutive(self, root):
+        self.longest(root)
+        return self.maxa
+
+    def longest(self, root):
+        """
+        longest ended at root
+        """
+        if not root:
+            return 0
+
+        maxa = 1
+        l = self.longest(root.left)
+        r = self.longest(root.right)
+        if root.left and root.val+1 == root.left.val:
+            maxa = max(maxa, l+1)
+        if root.right and root.val+1 == root.right.val:
+            maxa = max(maxa, r+1)
+
+        self.maxa = max(self.maxa, maxa)
+        return maxa
+
+    def longestConsecutive_error(self, root):
+        """
+        :type root: TreeNode
+        :rtype: int
+        """
+        if not root:
+            return 0
+
+        maxa = 1
+        l = self.longestConsecutive(root.left)
+        r = self.longestConsecutive(root.right)
+        maxa = max(maxa, l, r)
+        if root.left and root.val + 1 == root.left.val:
+            maxa = max(maxa, l+1)
+        if root.right and root.val + 1 == root.right.val:
+            maxa = max(maxa, r+1)
+
+        return maxa