问题 单项选择题

对下列二叉树

进行中序遍历的结果是()

A、ACBDFEG

B、 ACBDFGE

C、 ABDCGEF

D、 FCADBEG

答案

参考答案:A

解析:

二叉树的中序遍历递归算法为:如果根不空,则(1)按中序次序访问左子树;(2)访问跟结点;(3)按中序次序访问右子树。否则返回。本题中,根据中序遍历算法,应首先按照中序次序访问以C为根结点的左子树,然后再访问根结点P,最后才访问以E为根结点的右子树。遍历以C为根结点的左子树同样要遵循中序遍历算法,因此中序遍历结果为ACBD;然后遍历根结点F;遍历以E为根结点的右子树,同样要遵循中序遍历算法,因此中序遍历结果为EG。最后把这三部分的遍历结果按顺序连接起来,中序遍历结果为ACBDFEG。因此,本题的正确答案是A。

完形填空
完形填空。

     The trip to that city was eye-opening for everyone, and near its end, all the young people in our group
began to reflect on what it had meant. We   1   the first night we had arrived. We had all gone into the markets
of the city   2   the young people could experience its energy. But what we actually saw simply   3   us all—
the rundown houses, the children in rags, the people begging for money … Walking home,   4   under a low
bridge, we came across   5   families of homeless people seeking a bit of dry ground to sleep on   6   the night.
We had to step over bodies as we found our way through the darkness.
     The poverty (贫困) was   7    than anything my young companions had ever imagined. Back in the hotel,
an air of sadness settled over the group. Many   8   and cried. Spending time in this   9   moves a person to
care about humanity.
     That evening, our group spent hours talking about what we had  10 . Gently, I encouraged everyone to talk
about the difficult  11  that day’s discoveries had inspired. Sitting together  12  a circle as everyone had a
chance to speak, we all began to realize that  13  of us was alone in our struggle to cope with our reactions.
     Based on my  14  in poverty-stricken areas, I suggested that  15  the emotions we had were painful, they
could also be important in helping us to move forward. We all  16  that we had seen things that should never
be allowed to happen.  17 , what could we do about it? Together, we began to brainstorm ways we could help
to ease the  18  we had seen. As I encouraged group members to focus on  19  they could do, a sense of
determination  20  the previous sadness. Instead of despair, these young people began to feel a call to action.

( )1. A. put up with  
( )2. A. now that     
( )3. A. puzzled      
( )4. A. marching     
( )5. A. entire       
( )6. A. beyond       
( )7. A. stronger     
( )8. A. gave up      
( )9. A. environment  
( )10. A. inspected   
( )11. A. feelings    
( )12. A. along       
( )13. A. neither     
( )14. A. experiences 
( )15. A. once        
( )16. A. supposed    
( )17. A. Surely      
( )18. A. burden      
( )19. A. how         
( )20. A. replaced    
B. got back to 
B. so that     
B. annoyed     
B. running     
B. normal      
B. with        
B. deeper      
B. broke down    
B. hotel       
B. attempted   
B. decisions   
B. around      
B. either      
B. schedules   
B. while       
B. advised     
B. Rather      
B. suffering   
B. where       
B. changed     
C. looked back on  
C. as if          
C. embarrassed    
C. passing        
C. average        
C. till           
C. worse          
C. set off        
C. house          
C. witnssed       
C. thoughts       
C. by             
C. none           
C. data           
C. since          
C. confirmed      
C. Now            
C. anxiety        
C. what           
C. covered        
D. made up for 
D. even if     
D. shocked     
D. moving      
D. general     
D. for         
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D. held on     
D. background              
D. challenged  
D. impressions 
D. in          
D. each        
D. position    
D. unless      
D. agreed      
D. Indeed      
D. difficulty  
D. when        
D. improved    
名词解释