Create infix_to_postfix.py

Author: ashwek

Mathematical_Algorithms/src/infix_to_postfix.py

@@ -0,0 +1,52 @@
+"""
+Output:
+
+Enter an Infix Equation = a + b ^c
+ Symbol  |  Stack  | Postfix
+----------------------------
+   a     |         | a
+   +     | +       | a
+   b     | +       | ab
+   ^     | +^      | ab
+   c     | +^      | abc
+         | +       | abc^
+         |         | abc^+
+
+	 a+b^c -> abc^+
+"""
+
+def infix_2_postfix(Infix):
+    Stack = []
+    Postfix = []
+    priority = {'^':3, '*':2, '/':2, '%':2, '+':1, '-':1}       # Priority of each operator
+    print_width = len(Infix) if(len(Infix)>7) else 7
+
+    # Print table header for output
+    print('Symbol'.center(8), 'Stack'.center(print_width), 'Postfix'.center(print_width), sep = " | ")
+    print('-'*(print_width*3+7))
+
+    for x in Infix:
+        if(x.isalpha() or x.isdigit()): Postfix.append(x)       # if x is Alphabet / Digit, add it to Postfix
+        elif(x == '('): Stack.append(x)                         # if x is "(" push to Stack
+        elif(x == ')'):                                         # if x is ")" pop stack until "(" is encountered
+            while(Stack[-1] != '('):
+                Postfix.append( Stack.pop() )                   #Pop stack & add the content to Postfix
+            Stack.pop()
+        else:
+            if(len(Stack)==0): Stack.append(x)                  #If stack is empty, push x to stack
+            else:
+                while( len(Stack) > 0 and priority[x] <= priority[Stack[-1]]):      # while priority of x is not greater than priority of element in the stack
+                    Postfix.append( Stack.pop() )                                   # pop stack & add to Postfix
+                Stack.append(x)                                 # push x to stack
+
+        print(x.center(8), (''.join(Stack)).ljust(print_width), (''.join(Postfix)).ljust(print_width), sep = " | ")         # Output in tabular format
+
+    while(len(Stack) > 0):                                  # while stack is not empty
+        Postfix.append( Stack.pop() )                       # pop stack & add to Postfix
+        print(' '.center(8), (''.join(Stack)).ljust(print_width), (''.join(Postfix)).ljust(print_width), sep = " | ")         # Output in tabular format
+
+    return "".join(Postfix)             # return Postfix as str
+
+Infix = input("\nEnter an Infix Equation = ")       #Input an Infix equation
+Infix = "".join(Infix.split())                      #Remove spaces from the input
+print("\n\t", Infix, "->", infix_2_postfix(Infix))