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