Find the prefix

[plain hinge]

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[fluid salmon]

@swift vessel it's not really helpful to do people's assignment for them

[swift vessel]

@fluid salmon It was very simple question that's why i choose to answer it

[fluid salmon]

not simple when you don't understand it

[iron ore]

it's also technically against the rules

#rules 5. We're happy to help you learn, however, we do not condone academic dishonesty. We will not take your tests for you or write programs for you. Likewise avoid giving full solutions to problems when helping other members.

[swift vessel]

Sorry i have deleted it

[fluid salmon]

@ocean sequoia what have you tried so far?

[ocean sequoia]

yea i have tried

but it is kind of weird

• • 3 4 / - 5 2 + 6 1

this is wat i got

[fluid salmon]

I think that looks correct

[ocean sequoia]

actually it is wrong

[fluid salmon]

how so?

oh yeah the order of the precedence is wrong for * and /

[swift vessel]

This is wrong because your division should be performed at last

So division operator should come first and then multiplication

[ocean sequoia]

if i change that infix to postfix i will get 3 4 + 5 2 - * 6 1 + /

and how can i reverse that to get prefix

[swift vessel]

@ocean sequoia We cannot obtain prefix by reversing postfix expression

Just think logically

[ocean sequoia]

i am writing this code

On internet, most people will do like reverse infix then postfix then reversed postfix to get prefix

[swift vessel]

@ocean sequoia Ohh you want to code it , i thought you are just converting it manually

Then you will first have to reverse the expression , convert it to postfix and then reverse it again

[ocean sequoia]

this is wat i do

reverse

postfix

reverse

[swift vessel]

The problem is occurring because of associativity rules

When you reverse the expression at first stage, the order of operators with similar precedence also reverses

In your case '/' comes left side and '*' goes right side, but here * should evaluate first because in original expression * was left side

So, whenever you are converting reversed expression into postfix, you should not pop out operators with similar precedence

So, your postfix should be like this :
16+25-43+*/

@ocean sequoia You got my point?

[ocean sequoia]

yea i got it

[swift vessel]

great lmk if you have any other doubts with this

[ocean sequoia]

So i got this problem
Infix : 59+ 107 * 83 7291 / ( 27 - ( 112 * 153 ) * ( 111 + 76 ) )
Reverse : ( ( ( 67 + 111 ) * ( 351 * 211 ) - 72 ) / 19 * 27 * 38 * 701 + 95 )
postfix: 67 111 + 351 211 * * 72 - 19 27 38 701 * * 95 + * /
Reverse postfix: / * + 59 * * 107 83 72 91 - 27 * * 112 153 + 111 76 (This is wat i got)
Prefix(Answer) : + 59 / * * * 107 83 72 91 - 27 * * 112 153 + 111 76

[swift vessel]

@ocean sequoia Can you clearly show me what is the infix expression? because i can't see multiplication operators in your infix expression, but i can see them in postfix expression

Ok i think you have wrote it ,but it is not visible to me

[ocean sequoia]

59+ 107 * 83 *72 *91 / ( 27 - ( 112 * 153 ) * ( 111 + 76 ) )

[swift vessel]

Okk it is visible now

[ocean sequoia]

sorry

https://onlinegdb.com/QDsgEvDbT

here my code

u can take a look at it

[swift vessel]

@ocean sequoia Yes sure

[ocean sequoia]

btw it kind basic

cuz i just started learning

[swift vessel]

@ocean sequoia it's okay

@ocean sequoia Why are you reversing the numbers also

don't reverse the numbers , just reverse the expression

For example ,in reversed expression 76 should be 76 only

It will not be 67

[ocean sequoia]

but it is still fine isnt it ?

[swift vessel]

Yeah I guess so, because you are again reversing the expression

[ocean sequoia]

yea

[swift vessel]

Your postfix of reverse expression is wrong though

Wait let me go through the code first

Your post fix of reverse expression should be: 67 111 + 351 211 * * 72 - 19 27 38 701 * * */ 95 +

Because when you reach at "+" , you will have to pop out '*' and append to the output

Because * have greater precedence than +

[ocean sequoia]

yea but with my code idk where to fix

[swift vessel]

let me check

@ocean sequoia Why are you checking if operator.top() is empty at line 75 and 116?

[ocean sequoia]

i dont see it

[swift vessel]

Ohh, i think some glitch, after copying it

[swift vessel]

@ocean sequoia It is very complex, but issue i can see is you don't have any loop inside the main loop, which means, whenever any lower precedence operator comes, it will not able to pop out all the operators with higher precedence from the stack

[ocean sequoia]

yea i also think like that

[swift vessel]

In this expression you have to pop out all * operator when + comes

You can try to make your code simpler, it will be easy to understand and debug for you also

My suggestion is, define one function which will deal with the precedence

[ocean sequoia]

oh i got it

thank you

[swift vessel]

for example: if( op=='^'){ return 3} if(op=='*){ return 2 } something like this

[plain hinge]

@ocean sequoia Has your question been resolved? If so, run !solved :)

[ocean sequoia]

not yet =))

[ocean sequoia]

!solved

[plain hinge]

Thank you and let us know if you have any more questions!

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