From two arguments which are the sequence of preorder and postorder, 
  construct the corresponding process tree. The output should be in postorder.


                  a
               /  |  \
              c   b   y
             / \
            x   t

  For tree shown above, the output for your program may be like
  as follows.

-----------------------------------------------------------------------
$ echo $$ 
14436     <------- pid of the shell
$ 
$ ./a.out acxtby xtcbya
Hello, I'm 14500, my parent is 14499, and my name is x
Hello, I'm 14501, my parent is 14499, and my name is t
Hello, I'm 14499, my parent is 14498, and my name is c
Hello, I'm 14502, my parent is 14498, and my name is b
Hello, I'm 14503, my parent is 14498, and my name is y
Hello, I'm 14498, my parent is 14436, and my name is a
$