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},
return its zigzag level order traversal as:
confused what "{1,#,2,3}" means? >
read more on how binary tree is serialized on OJ.
The serialization of a binary tree follows a level order traversal, where '#' signifies a path terminator where no node exists below.
Here's an example:
The above binary tree is serialized as "{1,2,3,#,#,4,#,#,5}".
題意：層次遍歷1顆樹，奇數(shù)層的時(shí)候翻轉(zhuǎn)。
思路：還是利用隊(duì)列層次遍歷，多1個(gè)判斷是不是翻轉(zhuǎn)的標(biāo)記就好了，還有就是java是援用傳遞的，所以每次都要重新聲明1個(gè)對(duì)象，不然ans里面都是指向同1塊內(nèi)存。
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