pro4 solved without parathesis

Author: yyl

unit3/infix_input.txt

@@ -0,0 +1,4 @@
+5 + 9 * 2 + 6 * 5 =
+5 * 8 + 6 / 10 =
+5 - 8 - 9 =
+5 * 8 * 9 =

unit3/output.txt

@@ -1,5 +1,4 @@
-(((5.5 + 9) * 2) + (6 * 1.5)) = 
-(5.5 + 5) = 
-(((5.5 / 2) + 4) * 5) = 
-(5 ^ 2) = 
-(-5 + 5) = 
+5 9 2 * + 6 5 * + = 
+5 8 * 6 10 / + = 
+5 8 - 9 - = 
+5 8 * 9 * = 

unit3/pro4.py

@@ -0,0 +1,81 @@
+from opus7.stackAsLinkedList import StackAsLinkedList
+
+class Algorithms(object):
+
+  def __init__(self):
+    self.stack = StackAsLinkedList()
+
+  def calculator(self, input, output):
+    operators = ["+", "-"]
+    priors = ["*", "/"]
+    for line in input.readlines():
+      flag = 0
+      size = 0
+      for word in line.split():
+        '''
+        match_left = re.search(r'\(', word)
+        match_right = re.search(r'\)', word)
+        if match_left:
+          self.stack.push(word[1:])
+          flag = 1
+        if match_right:
+          self.stack.push(word[:-1])
+          '''
+        if word in operators:
+          print "it is an operator: ", word
+          while size >= 3:
+            arg2 = self.stack.pop()
+            op = self.stack.pop()
+            arg1 = self.stack.pop()
+            size -= 3
+            self.stack.push("%s %s %s" % (arg1, arg2, op))
+            size += 1
+            print "push ", arg1, arg2, op
+          self.stack.push(word)
+          print "pushing ", word
+          size += 1
+          flag = 0
+        elif word in priors:
+          print "it is a prior: ", word
+          # indicating there are a pair of arg1 * arg2 in stack
+          # waiting for poping out
+          if flag == 1 and size >= 3:
+            arg2 = self.stack.pop()
+            op = self.stack.pop()
+            arg1 = self.stack.pop()
+            size -= 3
+            self.stack.push("%s %s %s" % (arg1, arg2, op))
+            size += 1
+            print "push ", arg1, arg2, op
+          # push the operator itself
+          self.stack.push(word)
+          print "pushing ", word
+          size += 1
+          flag = 1
+        elif word == "=":
+          print "it is ="
+          while size >= 3:
+            arg2 = self.stack.pop()
+            op = self.stack.pop()
+            arg1 = self.stack.pop()
+            size -= 3
+            self.stack.push("%s %s %s" % (arg1, arg2, op))
+            size += 1
+            print "push ", arg1, arg2, op
+          output.write("%s %s %s = \n" % (arg1, arg2, op))
+          print "writing into files", arg1, arg2, op
+        else:
+          print "it is number: ", word
+          self.stack.push(word)
+          print "pushing ", word
+          size += 1
+
+
+
+
+
+
+a = Algorithms()
+a.calculator(open("infix_input.txt", 'r'), open("output.txt", 'w+'))
+
+