Question
Python problem! builds the expression tree from expr. Do not change other functions. Test code is given at the end. Thank you very much! class
Python problem! builds the expression tree from expr. Do not change other functions. Test code is given at the end. Thank you very much!
class expressionTree: # constructTree(expr) builds the expression tree from expr # Here you can assume: # expr is an arithmetic expression with an answer value # The first non-space symbol is not "-" # (because we can add "0" to the left if so) # # getExpr() to reconstruct expr from the tree # # revPolish() to get the reverse polish notatation # # and maybe more...
class treeNode: def __init__(self, value, lchild, rchild): self.value, self.lchild, self.rchild = value, lchild, rchild
def __init__(self): self.treeRoot = None
#utility functions for constructTree def mask(self, s): # The function empties the inside of every outermost parentheses pair # and return it as a string # # e.g. s = ( 2 + 3^2 -(2-4)) + 2 - (-1 + 1/7) # It returns ( ) + 2 - ( ) # # --- code ----#
#Build expression tree from expr, set it to self.treeRoot def constructTree(self, expr): temp = 1 #input = the expression tree whose root is self.treeRoot #output = reconstructed arithmetic expression as a def getExpr(self): temp = 1 #input = the expression tree whose root is self.treeRoot #output = string that is the reverse polish notation def revPolish(self): temp = 1
# To check the mask function e = expressionTree() s =" ( 2 + 3*(2- 1/3))+ 2 - ((5-2/3)*3 - 2)" print(e.mask(s)) # should print # ( )+ 2 - ( )
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