3.9 Evaluation of Prefix and Postfix expressions using Stack | Data Structures

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In this lecture I have described how we can evaluate prefix and postfix expressions efficiently using stack data structure.

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Thanks so much!! I was about to flunk my ACSL contest but then I watched this video. Thanks a lot again god bless you, madam.

anthamh

you are just making our life easier. Thank you.

official-ali

Hi, i love your teaching style where you have shared so technically, thanks for effective lecture on prefix and postfix.

SaifulIslam-enji

Thank you so much mam you are making DSA a easier subject

keerthanarajendran

Beauty with brain ❤️❤️😍
Edit 1: my comment got highlighted 😍❤️

shivamchhabra

Madam you are very talented and you can teach very clearly, this lecture series is great help to me, thank you lot👍

hashensenevirathna

In previous video u said first we have to reverse the equation n solve from right to left but here you have directly started with right to left without reverse

HEENARANA-ijmy

Nice explanation !! Can u plzz give code implementation also.

vaishnavidongare

Thanks for the Lecture, in addition to it, "-+2*34/[16]^23" in coding it's a must to put a type brakets to define a two or more digit number, otherwise it'll fail; here an example with C# :

public double evaluateString)
{

StringBuilder appendBuilder= new StringBuilder();
int length = evaluateString.Length;

for (int i = length - 1; i >= 0; i--)
{
string c =

if (char.IsDigit(c, 0))
{
double term = Convert.ToSByte(c);
Push(term);
}
else if (c=="]")
{
char join = evaluateString[--i];
while (join!='[')
{
appendBuilder.Insert(0, join);
join = evaluateString[--i];
}

appendBuilder.Clear();
}
else
{
switch (c)
{
case "^":
double first = Pop();
double second = Pop();
double result = Math.Pow(first, second);
Push(result);
break;
case "*":
first = Pop();
second = Pop();
result = first * second;
Push(result);
break;
case "/":
first = Pop();
second = Pop();
result = first / second;
Push(result);
break;
case "+":
first = Pop();
second = Pop();
result = first + second;
Push(result);
break;
case "-":
first = Pop();
second = Pop();
result = first - second;
Push(result);
break;
}
}
}

return Pop();
}

sabitkondakc