Binary Tree Zigzag Level Order Traversal - LeetCode
2015-03-30 20:49
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Binary Tree Zigzag Level Order Traversal - LeetCode
题目:
Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from left to right, then right to left for the next level and alternate between).
For example:
Given binary tree {3,9,20,#,#,15,7}
,
3
/ \
9 20
/ \
15 7
return its zigzag level order traversal as:
[
[3],
[20,9],
[15,7]
]
分析:
这道题目的基本思想和 BinaryTree Level Order Traversal (点击打开链接)一样,只是最后加一个对于i%2 ==1 的列表项的倒序。
代码:
class Solution: # @param root, a tree node # @return a list of lists of integers def zigzagLevelOrder(self, root): if not root: return [] res = [[]] self.bfs(root,res,0) for i in range(len(res)): if i%2 == 1: res[i]=res[i][::-1] return res def bfs(self,root,l,i): if not root: return if i == len(l): l.append([]) l[i].append(root.val) self.bfs(root.left,l,i+1) self.bfs(root.right,l,i+1)
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