已知一棵二叉树前序遍历和中序遍历分别为ABDECCPH和DBGEACHF，则该二叉树的后序遍历为
A．GEDHFBCA
B．DGEBHFCA
C．ABCDEFGH
D．ACBFEDHG
参考答案：B
解析：【解析】利用前序和中序遍历的方法可以确定二叉树的结构，具体步骤如下：①前序遍历的第一个结点A为树的根结点；②中序遍历中A的左边的结点为A的左子树，A右边的结点为A的右子树；③再分别对A的左右子树进行上述两步处理，直到每个结点都找到正确的位置。
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| That cold January night, I was growing sick of my life in San Francisco. There I was, __1__ home at one in the morning after a(n) __2__ practice at the theatre. With __3__ night only a week away, I was still learning my __4__. I was having __5__ dealing with my parttime job at the bank and my acting at theatre at the same time. As I walked, I thought seriously about __6__ both acting and San Francisco. __7__ had become too much for me. As I walked down empty streets under tall buildings, I felt very __8__ and cold. I began running, both to keep warm and to keep away from any possible robber(抢劫犯). Very few people were still out except a few sadlooking homeless people under blankets. About a block from my apartment, I heard a __9__ behind me. I 10 quickly, half expecting to see someone with a knife or a gun. The street was 11 . All I saw was a streetlight. 12 , the noise had made me nervous, so I started to run faster. Not until I reached my apartment building and unlocked the door did I realize what the noise had been. It had been my 13 falling to the sidewalk. 14 I wasn't cold or tired anymore. I ran out of the door and back to where I'd heard the noise. Although I searched the sidewalk 15 for fifteen minutes, my wallet was nowhere to be found. Just as I was about to give up the search, I heard the garbage truck(垃圾车) 16 to the sidewalk next to me. When a voice called from the inside, "Alisa Camacho?" I thought I was 17 . How could this man know my name? The door opened, and out jumped a small redhaired man with a(n) 18 look in his eyes. "Is this what you're looking for?" he asked, holding up a small square shape. It was nearly 3 am by the time I got into bed. I wouldn't get much sleep that night, but I had gotten my wallet back. I also had gotten back some 19 of city life. I realized that the city couldn't be a bad place 20 people were willing to help each other. | ||||
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