Infix To Postfix using Stack

Author: OmkarPathak

Stack/P01_InfixToPostfix.py

@@ -0,0 +1,48 @@
+# Author: OMKAR PATHAK
+
+import Stack
+
+def isOperand(char):
+    return (ord(char) >= ord('a') and ord(char) <= ord('z')) or (ord(char) >= ord('A') and ord(char) <= ord('Z'))
+
+def precedence(char):
+    if char == '+' or char == '-':
+        return 1
+    elif char == '*' or char  == '/':
+        return 2
+    elif char == '^':
+        return 3
+    else:
+        return -1
+
+def infixToPostfix(myExp, myStack):
+    postFix = []
+    for i in range(len(myExp)):
+        if (isOperand(myExp[i])):
+            postFix.append(myExp[i])
+        elif(myExp[i] == '('):
+            myStack.push(myExp[i])
+        elif(myExp[i] == ')'):
+            topOperator = myStack.pop()
+            while(not myStack.isEmpty() and topOperator != '('):
+                postFix.append(topOperator)
+                topOperator = myStack.pop()
+        else:
+            while (not myStack.isEmpty()) and (precedence(myExp[i]) <= precedence(myStack.peek())):
+                postFix.append(myStack.pop())
+            myStack.push(myExp[i])
+
+    while(not myStack.isEmpty()):
+        postFix.append(myStack.pop())
+    return ' '.join(postFix)
+
+if __name__ == '__main__':
+    myExp = 'a+b*(c^d-e)^(f+g*h)-i'
+    myExp = [i for i in myExp]
+    print('Infix:',' '.join(myExp))
+    myStack = Stack.Stack(len(myExp))
+    print('Postfix:',infixToPostfix(myExp, myStack))
+
+    # OUTPUT:
+    # Infix: a + b * ( c ^ d - e ) ^ ( f + g * h ) - i
+    # Postfix: a b c d ^ e - f g h * + ^ * + i -