Reverse the infix string. Note that while reversing the string you must interchange left and right parentheses

Sazzad Hossen

Last update: Jan 4, 2022

Related tags

Miscellaneous prefix infix infixtopostfix-expression infixtoprefix prefixconvertion prefix-python prefix-convert

Overview

Infix-to-Prefix-Convertion-by-Python

def isOperator(c): return (not (c >= 'a' and c <= 'z') and not(c >= '0' and c <= '9') and not(c >= 'A' and c <= 'Z'))

def getPriority(C): if (C == '-' or C == '+'): return 1 elif (C == '*' or C == '/'): return 2 elif (C == '^'): return 3 return 0

def infixToPrefix(infix): operators = [] operands = []

for i in range(len(infix)):
    
    if (infix[i] == '(' ):
        operators.append(infix[i])

    elif (infix[i] == ')'):
        while (len(operators)!=0 and (operators[-1] != '(' )):
            op1 = operands[-1]
            operands.pop()
            op2 = operands[-1]
            operands.pop()
            op = operators[-1]
            operators.pop()
            tmp = op + op2 + op1
            operands.append(tmp)
        operators.pop()
    elif (not isOperator(infix[i])):
        operands.append(infix[i] + "")

    else:
        while (len(operators)!=0 and getPriority(infix[i]) <= getPriority(operators[-1])):
            op1 = operands[-1]
            operands.pop()

            op2 = operands[-1]
            operands.pop()

            op = operators[-1]
            operators.pop()

            tmp = op + op2 + op1
            operands.append(tmp)
        operators.append(infix[i])

while (len(operators)!=0):
    op1 = operands[-1]
    operands.pop()

    op2 = operands[-1]
    operands.pop()

    op = operators[-1]
    operators.pop()

    tmp = op + op2 + op1
    operands.append(tmp)
return operands[-1]

while(1): s = input("Infix Expression : ") print("Prefix Expression : ", infixToPrefix(s))

Step 1: Reverse the infix string. Note that while reversing the string you must interchange left and right parentheses. Step 2: Obtain the postfix expression of the infix expression Step 1. Step 3: Reverse the postfix expression to get the prefix expression

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Reverse the infix string. Note that while reversing the string you must interchange left and right parentheses

Related tags

Overview

Infix-to-Prefix-Convertion-by-Python

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